Enhancing Olive Cultivation Resilience: Sustainable Long-Term and Short-Term Adaptation Strategies to Alleviate Climate Change Impacts

Abstract

Olive cultivation, an icon of Mediterranean agriculture, economy, and cultural heritage, faces significant challenges due to climate change and soil degradation. Climate projections indicate that altered precipitation patterns, rising temperatures, and increased frequency of extreme weather events will adversely affect olive tree growth, fruit quality, and yield. This review provides a novel perspective on addressing these challenges through both long-term and short-term adaptation strategies, emphasizing innovative products, advanced technologies, and practical solutions that must work synergistically and be tailored to regional conditions. Long-term practices refer to proactive strategies for enduring climate resilience, including cover cropping, mulching, soil amendments, and breeding programs which enhance soil health, improve water retention, and increase the trees’ resilience. Short-term strategies focus on immediate impacts, offering immediate stress relief and enhanced plant physiological responses, including optimized irrigation systems, pruning management, particle coating films, biostimulants, and plant growth regulators. The review underscores the importance of aligning agricultural practices with sustainability goals and evolving environmental policies and the education of farmers and policymakers. By integrating adaptive practices and technological advancements, the olive sector can better address climate challenges, contribute to global food security, and advance environmental sustainability.

1. Introduction

The olive tree is a perennial evergreen tree that belongs to the botanical family Oleaceae and genus Olea, with 30 species found worldwide. The most popular species is Olea europaea L., one of the oldest cultivated plants of the Mediterranean basin, with origins linked to the emergence of some of the most ancient civilizations [1,2]. Olive trees are native to tropical and warm temperate regions, and despite being widely distributed along the coastal regions of the eastern Mediterranean basin, they extend to several areas of the globe, including Asia, the Arabian Peninsula, northern Africa, South and North America, and Australia [3,4,5,6].

The socioeconomic importance of this crop is mainly attributed to olive oil production [3], which is the main source of fat in the recognized Mediterranean diet [4,7]. Olive oil is highly known for its numerous human health benefits, stemming from its balanced fatty acid composition and antioxidant properties [7]. Over the last few decades, the growing awareness of the nutritional value of olive oil has contributed to an increase in its consumption [8], as well as an expansion of olive tree cultivation areas over the last few decades [5,9]. During the 2021/2022 campaign, the latest available period, approximately 3.50 million tons of olive oil were produced worldwide, with over 90% originating from the Mediterranean region [8,10]. Spain leads global production, contributing around 45% of the world’s olive oil, followed by Italy (10%), Greece (7%), and Portugal (6%) [8]. In terms of exports, Spain also leads, accounting for 40% of global olive oil exports, followed by Italy (20%) and Tunisia (16%) [8]. On the import side, the United States is the largest importer, accounting for 34% of global imports, followed by Brazil with 9% [8]. This highlights how Mediterranean countries play a pivotal role in meeting global demand, making olive oil a major driver of international trade. Beyond its economic impact, olive cultivation supports millions of livelihoods, from small-scale family farms to large commercial operations. It is essential to the rural economies of many Mediterranean countries, helping to sustain agricultural employment and preserving cultural landscapes. Moreover, olive farms and oil production have become part of agrotourism, attracting visitors interested in the agricultural heritage and artisanal olive oil production.

Global climate change is one of the most pressing challenges of our time, with widespread impacts on ecosystems, agriculture, and food security [11]. Rising global temperatures, shifts in precipitation patterns, and an increased frequency of extreme weather events, such as droughts, floods, and heat waves, are already affecting agricultural productivity worldwide [11].

Considering the climate projections for the Mediterranean region, similar patterns are expected, including a significant reduction in precipitation, increases in temperature, and higher evapotranspiration rates [12,13]. Consequently, these changes will affect agricultural production, including olive cultivation, by influencing plant growth rates, transpiration, photosynthesis, and the reduction in crop productivity and will impact the quality of olive fruits and olive oil [9,14,15]. Moreover, the projections for the Mediterranean advise that the potentially cultivable areas for olive growing are expected to extend northward and to higher altitudes, while olive flowering may occur 11 ± 3 days earlier and crop evapotranspiration could increase by an average of 8% [16].

Another major threat to the sustainability of olive orchards is soil degradation, which is expected worsen due to climate change in the coming decades [17,18]. Climate change directly impacts soil functions, increasing erosion rates through frequent high-intensity rainfall events and inducing changes in organic carbon (OC) availability and nutrient cycling due to shifts in soil moisture and temperature regimes [19]. In this context, implementing appropriate sustainable practices is crucial for combating soil erosion and preserving soil health.

At the same time, conventional agricultural practices have also negatively impacted the environment, further exacerbating climate change [20]. In olive-growing regions in particular, activities such as conventional soil management (tillage), the use of fertilizers and pesticides, harvesting, transport, and olive milling, among others, generate and emit high levels of greenhouse gases (GHG) [21,22].

Considering the importance of the olive sector, it is necessary to improve its sustainability, profitability, resilience, and productivity in response to adverse climatic conditions. Therefore, it is crucial to study and implement effective agricultural adaptation strategies to address the challenges posed by climate change to olive cultivation. These strategies should also mitigate climate change by reducing GHG emissions and increasing C sequestration, as established by the Sustainable Development Goals for 2030 [23]. Adaptation strategies for olive cultivation, including practices such as cover cropping, mulching, soil amendments, breeding programs, optimized irrigation systems, pruning management, the use of particle coating films, biostimulants, and plant growth regulators, have been shown to effectively enhance plant responses to adverse conditions and boost overall resilience [24,25,26,27,28,29,30,31].

This review offers a novel perspective on addressing the climatic challenge impacts on olive cultivation through both long-term and short-term adaptation strategies that must work synergistically. By focusing on innovative products, technologies, and practical solutions, the study can guide olive growers in implementing best practices to enhance resilience, and it provides a basis for developing policies that support sustainable olive production. We define ‘long-term strategies’ as those referring to proactive strategies aimed at adapting to climate change effects over time, and ‘short-term strategies’ as immediate actions taken to address the impacts of extreme weather events and provide rapid relief. To guide our investigation, we addressed the following research questions: (1) How does climate change impact olive cultivation? (2) What are the most effective long-term adaptation strategies for enhancing olive cultivation resilience to climate change over time and restoring agroecosystems? (3) What are the most effective short-term measures for immediate abiotic stress relief and improving olive tree responses? (4) What are the research gaps and potential policy and management implications for sustainable olive production? Thus, this review aims to explore the impacts of climate change on olive trees and to examine a range of sustainable agronomic practices that can mitigate these effects, improve climate resilience, and contribute to the overall sustainability and productivity of olive cultivation. The methodology for identifying the climate change impacts on olive cultivation and selecting adaptation strategies in this review involved a thorough and critical analysis of the literature across multiple disciplines pertinent to olive cultivation. We reviewed a wide array of sources, including peer-reviewed scientific articles, technical reports, books, and institutional websites. Strategies were chosen based on their prominence in highly cited and recent studies, as well as their demonstrated applicability and robustness of supporting evidence.

2. Climate Change Projections and Impacts on Olive Tree

Climate change is one of the most significant and far-reaching challenges that human societies face in this century [32]. In particular, the Mediterranean region is described as a climate change “hot spot” that is expected to experience substantial shifts in precipitation patterns and a rise in average temperatures [33,34,35]. These changes are already being noticed, with recent decades showing increased interannual variability in precipitation and temperature, as well as more frequent extreme climatic events across Europe, especially in the Mediterranean basin [17,35,36].

According to future projections, summer rainfall will likely be reduced by 10 to 30%. The reduction in precipitation, combined with increased evapotranspiration, may easily lead to critical water shortages in the Mediterranean region, where water resources are already at a critical level [34,35,37]. These conditions, which are expected to worsen in the Mediterranean area in the coming decades, will certainly intensify abiotic stress on plants and cause significant damage to crops [38], as described in detail below.

Abiotic stress factors generally have negative impacts on crop physiology, limiting growth and development, altering plant phenology, and reducing crop quality. High temperature and intense solar irradiance cause an exponential increase in the saturation vapor pressure of the air, resulting in a higher vapor pressure deficit (VPD) between the air and the leaf, which is defined as the difference between the saturation vapor pressure and the actual vapor pressure of the air [39,40]. Plants respond to high VPD with stomatal closure, but at the cost of reduced photosynthesis rates [39,41]. The decline in photosynthesis during drought periods is associated with both stomatal and non-stomatal limitations [42,43]. Under mild to moderate water deficit conditions, stomatal conductance decreases due to guard cell dehydration and chemical signals from the roots. As water deficit worsens, a biochemical limitation of the photosynthetic process occurs, where the potential rate for CO₂ assimilation is not reached, despite CO₂ saturation [44]. This reduction in photosynthesis leads to the absorption of more light energy than can be consumed by photosynthetic carbon fixation [42]. This excess energy can trigger an increase in the production of reactive oxygen species (ROS) [42,43]. To counteract this, plants initiate an antioxidant response, which includes the biosynthesis and accumulation of osmolytes, such as proline and sugars; this response is a well-known mechanism [45]. However, when ROS accumulation exceeds the antioxidant system’s capacity to remove it, oxidative damage can occur and affect cellular proteins and photosynthetic pigments [45]. As drought severity increases, CO₂ fixation and the net photosynthetic rate might be limited, leading to photosynthetic pigment degradation and perturbations of the photochemical processes [45,46]. Moreover, the increase in average nighttime temperatures is expected to raise plant respiration rates, leading to higher night transpiration rates and, consequently, to a reduction in water-use efficiency [47,48].

The olive tree is a sclerophyllous species and is well adapted to drought [46,49]. The ability to tolerate low soil water availability includes a series of anatomical, morphological, and biochemical strategies that act synergically against drought stress [45]. These adaptations mainly involve enhanced sclerophylly, with high foliar tissue density, the presence of thick cuticle and trichome layers, changes in cell wall elasticity to maintain cell turgor, and changes in foliar chemistry, through the accumulation of compatible solutes to decrease osmotic potential [45,50,51].

Nevertheless, the investment in drought tolerance strategies implies a metabolic cost, which seriously compromises growth and yield [2,49,50]. Generally, when water is not limited, plants invest a considerable fraction of their photoassimilates in the expansion of photosynthetic tissues. However, under drought stress, the investment in metabolic and physiologic mechanisms imposes a different pattern of allocation of assimilates, which results in negative repercussions for plant growth and yield [52,53].

On the other hand, one of the most expected consequences associated with global warming is the increase in minimum temperatures, especially in winter and early spring, which could also result in a decrease in chilling conditions [9,54,55]. Temperature acts as the main driver of olive tree phenology by regulating the release of the endo-dormancy period, after the accumulation of adequate cold units during winter and the release from the eco-dormancy period, whose duration is dependent on chill units cumulated from the end of endo-dormancy to the flowering stage [56]. The accomplishment of the chilling requirement plays a major role in determining olive flowering, since the accumulated exposure to cold temperatures enables plants to properly set inflorescence production when warmer temperatures arise [9,54,57]. Insufficient chilling results in a low fruit setting with detrimental consequences on final yields; sometimes, some olive varieties produce deformed floral buds and fruits under these circumstances [9,58]. In addition to serious disturbances in the physiology, growth, and yield of olive trees, an aggravation of alternate bearing and changes in the severity of the occurrence of pests and diseases, as well as in the quality of the olive products, is also expected [4,9,59,60,61]. Under adverse conditions, such as high temperature and water deficit, fruit ripening occurs earlier and more quickly and can result in more intense pre-harvest fruit fall [54]. This not only affects the timing of the harvest but also has significant implications for the oil accumulation process, altering the chemical composition, nutritional value, and sensory qualities of the olive oil, including its flavor, aroma, and stability [62]. In turn, these effects can seriously compromise the sustainability of orchards, leading to negative repercussions, such as abandonment of the economic activity, desertification, and aggravation of several environmental problems (Figure 1) [63].

3. Sustainable Practices to Adapt and Mitigate Climate Change

Sustainable agriculture aims to meet society’s food needs without compromising the ability of future generations to meet their own needs [64]. This concept is based on three main pillars: economic, environmental, and social [64].

Climate change is a global challenge that requires comprehensive and cross-sectoral action. Such action needs to take full consideration of the international goals and agreements, such as the 2030 Agenda for Sustainable Development and its universally agreed Sustainable Development Goals (SDG) [65]. Among the 17 SDGs, 4 are directly linked to food production and security: the dependence on synthetic fertilizers and pesticides to sustain high productivity (SDG 2); the decline in soil health due to unsustainable agricultural practices (SDGs 2 and 6); the loss of ecosystem services and agroecosystem stability driven by food production intensification and climate change (SDG 13); and the loss of biodiversity (SDG 15) [66]. This mainly requires the implementation of adaptation and mitigation strategies in agricultural systems. Adaptation alone is not enough to offset the effects of climate change and thus still needs to be supplemented by concerted mitigation efforts [67,68]. Adaptation plays a crucial role in addressing climate change in two ways: by assessing impacts and vulnerabilities and by developing and evaluating response strategies [69]. In turn, climate change mitigation is any action taken to permanently eliminate or reduce the long-term risks and hazards of climate change [70].

To effectively adapt to and mitigate the impacts of climate change on agricultural systems, a range of strategies have been implemented, which are broadly categorized into long- and short-term adaptation measures, based on their immediate and enduring effects on the crop (Figure 2). However, the integration of both long- and short-term strategies is essential to create a resilient agricultural system.

Long-term adaptation measures occur before the impact of climate change and usually aim to mitigate the source of climate change [71]. This involves changing conventional soil management systems, implementing cover crops and mulching, and applying soil amendments, which enhance soil health, increase carbon sequestration, and mitigate GHG emissions. Moreover, strategies such as breeding new drought-tolerant varieties can also promote long-term sustainability and resilience [71,72]. Short-term strategies are designed to provide rapid relief from the immediate impacts of climate change and extreme weather events. These measures include implementing efficient irrigation systems to combat drought, using physical barriers to protect crops from heat waves, and utilizing the exogenous application of plant growth regulators. Additionally, farmers can adjust pruning practices and enhance pest management to address the immediate threats posed by changing climate conditions.

The following sections of this review provide a detailed description of the most commonly used long- and short-term strategies in olive orchards.

4. Long-Term Adaptation Strategies

4.1. Cover Cropping

The inclusion of conservation practices, such as cover crops, into farming systems is a well-recognized strategy that ensures several ecosystem services, including the improvement of soil quality, nutrient cycling, pest regulation, and crop productivity [73,74,75]. Cover crops can enhance soil organic matter, C sequestration, soil permeability, mean aggregate size, and aggregate stability, contributing to increased soil structure and stability. These improvements lead to enhanced soil structure and fertility, regulation of water infiltration, soil erosion control, reduction in nutrient leaching, improvement of nutrient availability, reduced soil compaction, prevention of soil sealing and crusting, increase in biodiversity, and limitation of pests and weeds [74,76,77,78,79]. Therefore, the use of cover crops is recognized as an important soil management strategy, which allows a reduction in or even an elimination of the application of chemicals for weed and pests control, as well as a decrease in the mineral fertilizer needs [75,77].

However, some studies highlight potential competition between cover crops and main crops for water and nutrients, which can negatively impact crop yield and overall farm productivity [80,81]. Therefore, managing cover crops often requires trade-offs in an attempt to optimize their benefits and minimize their potential detrimental effects [78]. To select an appropriate cover crop, it is important to take into consideration several aspects, including the biological cycles and development stages of both the cover crop and the main crop, the type of cover crop, and the local climate conditions [76,82].

Cover crops can comprise a single species or a mixture of species and can consist of annual, biennial, or perennial vegetation [83]. They are classified as grasses (e.g., ryegrass and barley), brassicas (e.g., radishes and turnips), legumes (e.g., alfalfa, vetches, and clover), non-legumes (spinach, canola, and flax), and spontaneous vegetation [83].

The use of cover crops in olive orchards is usually associated with their ability to reduce the risks of soil erosion and runoff, especially when cultivated on slope terrains [81]. Thus, several authors have reported the use of cover crops in olive orchards. According to Rodrigues et al. (2019), the ideal cover crops for olive trees should be self-reseeding, early-maturing annual legumes: self-reseeding to maximize soil protection in the fall and reduce costs by avoiding frequent sowing; early-maturing to reduce competition for water; and legumes to grow better on poor soils, sequester more C in the soil, fix atmospheric nitrogen (N), and increase the biological activity of the soil [84]. The primary advantage of legumes compared to grasses, brassicas, and non-leguminous cover crops is their ability to obtain the N they need through a symbiotic relationship with bacteria in the nodules of the roots (rhizobia) that fix N from the atmosphere [85]. Martins et al. (2023) reported that using self-reseeding annual legume cover crops in a rainfed olive orchard improved the trees’ photosynthetic activity, nutritional status, soil moisture, and olive yield, compared to a conventional tillage practice. The authors attributed these positive effects to the asynchronous biological cycle of the cover crops relative to the olive trees, since the legumes nearly complete their life cycle just as the olive trees’ biological activity resumes [86]. Additionally, the early senescence of the legume species and the deposition of their residues, coupled with spring precipitation, initiated the decomposition process, thereby facilitating nutrient absorption by the olive trees. In turn, Gucci et al. (2012) described an increased olive fruit (by 65%) and oil yield (by 69%), as well as higher soil microporosity and organic carbon, with the use of a permanent natural cover [24]. Additionally, Repullo-Ruibérriz de Torres et al. (2021) studied different types of cover crops in an intensive olive grove and found that Brachypodium distachyon was particularly effective in increasing soil organic matter (SOM) and N availability at the soil surface [87].

One area that needs more attention is the optimization of cover crop management. The selection of appropriate cover crop species, the timing of planting and termination, and the management of their growth relative to the main crop’s lifecycle and different edaphoclimatic regions are critical factors that can influence the overall success of the practice. The economic viability of cover cropping in olive orchards also needs more in-depth study. While the ecological benefits are clear, the costs associated with establishing and maintaining cover crops need to be balanced against the long-term gains in soil health and productivity. This economic analysis is particularly important for small-scale farmers who may be more sensitive to short-term losses.

4.2. Mulching

The term “mulch” refers to any material other than soil or living vegetation that performs the function of a permanent or semi-permanent protective cover over the soil surface [88]. For this purpose, different materials can be used, such as vegetative residues, biological geotextiles, gravel, and crushed stones [89]. This agronomic practice is associated with several beneficial effects, including increased organic matter content, water retention, aggregate stability, soil erosion control, physical and chemical fertility, soil biology, and protection against extreme rainfall events [88]. Moreover, the conservation of soil moisture is one of the most evidenced advantages of mulching; this is particularly important under arid or semi-arid conditions, such as those of the Mediterranean region [90].

In olive orchards, this practice has mainly been implemented to address two major challenges affecting the Mediterranean region: controlling soil erosion and increasing organic matter content [88]. These are critical issues that significantly impact the sustainability and productivity of these agricultural systems. In this way, Bombino et al. (2021) studied the effects of soil mulching with pruning residues and found that it significantly reduced runoff and soil loss while increasing organic matter content [25]. In turn, Rodrigues et al. (2013) studied the effects of mulching legume cover crop residues in olive orchards and found that soil inorganic N availability increased only slightly and briefly, despite the high N content in the mulched phytomass. Additionally, the impact on olive yield and leaf N concentration was statistically significant only in a few instances. Considering the obtained results, the authors recommend some caution in the management of pure legume cover crops as a mulch in olive orchards due to the reduced transfer of N from legumes to olive trees [91]. In another study, Ferraj et al. (2011) compared the effects of different soil management practices on the yield and quality of a 25-year-old olive grove and reported that straw mulch treatment was more effective in increasing olive yield [92].

Some authors have also studied the combined effects of mulching with different irrigation regimes. For instance, Ahmed and Aly (2017) examined the effects of rice straw mulching combined with different deficit irrigation levels on the growth and yield of mature olive trees. The study found that applying mulching along with a 70% irrigation regime significantly improved yield, vegetative growth parameters, and flowering density [93]. In addition, Gholami et al. (2023) reported that organic mulches, such as animal manure and olive pomace, combined with irrigation, significantly improved tree water status and yield [94].

While mulching offers numerous benefits for soil health and crop productivity, more in-depth research is needed to optimize its application. This includes understanding the nutrient dynamics of different mulch materials and the long-term effects on soil and crop performance. Additionally, the interaction between mulching and irrigation practices is an area of ongoing research, as mulching can play a significant role in water management strategies. Furthermore, the establishment of studies to evaluate and compare the effects of mulching across different regions and climates is crucial for determining the effectiveness of specific mulching practices in relation to local soil and climatic conditions. The economic feasibility of mulching, particularly in large-scale olive orchards or resource-limited regions, also requires further exploration.

4.3. Soil Amendments

Soil amendments are used in agriculture to support plant growth and development, specifically by adding organic and inorganic nutrients to the soil and improving soil physicochemical and biological properties [95]. These materials benefit agricultural systems by controlling soil degradation, promoting soil remediation, enhancing soil–air–water relations, and improving drainage and aggregation [96,97,98]. In addition to improving the availability of nutrients for crops, soil amendments also increase the competitiveness against weeds and the defense against pests and diseases [96].

Soil amendments can be applied to the upper layers of soil, where root systems are developed. They can be classified according to their origin (natural or synthetic) and composition (organic or inorganic) [97]. Organic soil amendments are those that derive from living organisms (e.g., plants and animals), and are well known to improve infiltration and water retention, promote aggregation, enhance microbial activity, and increase resistance to the crusting and compaction of soil with SOM [96]. Some examples of organic conditioners include crop residues, manures, peat, biochar, coffee grounds, olive mill wastes, farmyard manure, and sawdust [96]. Inorganic soil amendments are either mined or manufactured byproducts, occurring naturally or synthetically. Materials such as gypsum, lime, zeolites, pyrites, fly ash, and dolomite are examples of inorganic soil amendments, which can be applied to adjust soil acidity and ameliorate soil quality as most of them are alkaline materials abundant in Si, Ca, K, and Mg [99]. In turn, polymers are a typical example of synthetic soil conditioners and can be applied cost-effectively at a low rate. Other soil conditioners include industrial wastes, enzymes, microorganisms, and activators [96].

As this review discusses the implementation of sustainable practices, we provide a detailed description of the use of organic and natural soil amendments, such as biochar, zeolites, and olive mill wastes.

4.3.1. Biochar

Biochar is a carbon-rich solid produced by biomass pyrolysis with little or no oxygen, and it exhibits a porous carbonaceous structure, many functional groups, and an aromatic surface [100,101]. Among biochar components, the carbonaceous and ash materials constitute the solid part, and a mix of air and volatiles constitute the gaseous fraction [102]. It is characterized by a heterogeneous composition and its surfaces can exhibit both hydrophilic or hydrophobic and acidic or basic properties, allowing the reaction with soil components [102].

The type of biochar produced depends on the feedstock being used, the temperature, and the rate of heating [100,103]. Diverse types of feedstocks can be used to produce biochar, such as woodchips, organic wastes, plant residues, and poultry manure [100,101]. The common pyrolysis time and temperature range from 60 to 240 min and from 300 to 700 °C, respectively [100]. Taking into account that biochar properties vary depending on the production technology and biomass feedstock, special care has to be taken when producing biochar for agricultural soil amendment [104].

Biochar presents important physicochemical properties, such as high porosity, specific surface area, absorption capacity, cation exchange capacity (CEC), and stability [100,101,105]. In detail, the porosity of this material promotes soil aeration and hydrology and acts as a hotspot for microbial activity, which increases the abundance of soil biota [102]. The extraordinary water absorption ability is due to its void content, which allows the increase in soil water-holding capacity [102]. In turn, the CEC of biochar indicates its ability to adsorb cations such as NH₄⁺ and Ca²⁺, which are essential nutrients for plants, and it also contributes to the reduction in nutrient leaching losses from soils [100]. Thus, the soil nutrient availability and plant uptake increase, which confers a fertilizer character [102,106]. An increase in pH in acidic soils has been also demonstrated and is attributed to the decreased exchangeable Al³⁺ in soil due to its chelation with organic compounds from the biochar [104]. Another important application of biochar is its ability to sequester C. By charring the organic material, much of the C becomes “fixed” into a more stable form, and when the resulting biochar is applied to soils, the C is effectively sequestered [105].

Despite being a very promising strategy, few studies have addressed the use of biochar in olive orchards and reported its effects on plant performance, product quality, and soil properties. A study conducted by De la Rosa et al. (2022) found that using biochar made from dry olive pomace as a soil amendment in a super-intensive olive grove increased the net photosynthesis rate, intrinsic water use efficiency, electron transport rate, and olive yield. The authors concluded that applying biochar to the soil could reduce the amount of irrigation water needed while maintaining olive yields [26]. Sánchez-García et al. (2016) reported that applying biochar alone as a soil amendment in a commercial organic olive grove did not affect N dynamics but significantly increased soil C. Moreover, combining biochar with compost created a synergistic effect, enhancing denitrifying enzyme activity and increasing N₂O emissions [107]. In turn, Lopes et al. (2022) studied the effect of biochar application on a non-irrigated olive orchard of mature trees. While they found no impact on the trees’ productive performance, there was a significant improvement in the soil, marked by an increase in organic matter and CEC [108]. On the other hand, Martins et al. (2022) explored the effect of combining biochar application with fertilizer on olive yield, fruit, and oil composition and quality. They found no impact on crop yield; however, the fruits from the biochar treatment had a higher content of polyphenols with high nutritional value, such as 3,4-dihydroxyphenylglycol (an increase of 25.6%), oleuropein (84.8%), and rutin (11.6%) [109].

4.3.2. Natural Zeolites

Zeolites are crystalline and hydrated aluminosilicates, naturally formed in the reaction of volcanic ash with surface water or groundwater [110,111]. They can also arise in the non-volcanic environment during an interaction between the saline soil particles and strong basic solutions [111,112]. These aluminosilicates are structurally based on a three-dimensional anionic network of SiO₄ and AlO₄ tetrahedra linked to each other by the sharing of all the oxygen atoms [112,113]. Due to their inner structure, zeolites are characterized by unique physical and chemical properties [112,114,115]. The most general physical properties of the zeolites are bulk density, porosity and specific gravity. On the other hand, the CEC, adsorption properties, ion selectivity, pH, molecular sieving, and catalytic activity of zeolites are some of the principal chemical properties reported [116]. In particular, the porous structure of zeolite crystals allows the selective penetration of particles of a certain size, the dehydration and hydration of the crystals, the exchange of water for other molecules, and the exchange of ions. Therefore, zeolites can accommodate new cations (mainly Na⁺, K⁺, Mg²⁺, and Ca²⁺), water molecules, and even small organic molecules. In addition, zeolites can retain nutrients in the topsoil, which are slowly and gradually leached from the soil [116]. Due to their ability to hydrate and rehydrate, they can maintain a proper water balance in the soil and prevent the drying of soils and soil-like substrates [117].

On the other hand, natural and synthetic zeolites have been used to reduce the bioavailability of heavy metals in the soil [110]. The use of zeolites in acidic soils causes an increase in pH that significantly reduces the heavy metal solubility and bioavailability for plants [118].

For these reasons, zeolites have been extensively used in agriculture as soil amendments and slow-release fertilizers [114]. One of the main advantages of using zeolite additives in fertilizers is their beneficial effect on the retention of nutrients in the soil and the consequent use of smaller doses of fertilizer, which is associated with a reduction in the cost of crop production [119]. In this regard, Medoro et al. (2022) investigated the effect of zeolite-rich tuff soil amendment on young olive trees to improve the efficiency of N fertilizers and reduce their use. The authors found that incorporating zeolite-rich tuff reduced fertilizer requirements by up to 50% and improved N use efficiency [120]. In addition, Perez-Caballero et al. (2008) conducted an experiment to examine the effect of using zeolites in organic olive groves on soil and tree nutrient status. The preliminary results showed that zeolites significantly increased N availability in the soil and K levels in both the soil and leaves [121]. In another study, Martins et al. (2023) evaluated the effect of combining zeolites with an early-maturing annual legume cover crop and found positive impacts on photosynthetic activity, tree nutritional status, soil moisture, and olive yield compared to a conventional tillage treatment. At the soil level, the combination of zeolites with cover crops was significantly more effective in improving soil health indicators, including the availability of N, P, and B, CEC, and microbiological activity [86]. Additionally, this combination enhanced the polyphenolic concentration of olive fruits and oil, as well as the quality indicators of olive oil [122].

Al-tabbal et al. (2020) explored the effects of using volcanic zeolite tuff on olive trees in a silty clay soil and found a positive effect on tree growth parameters, leaf water potential, soil N and P levels, and overall soil chemical parameters [123]. In turn, Lopes et al. (2020) examined the effects of zeolites on the growth of young and rainfed olive trees planted in very acidic soil. The results indicated that the effect of zeolites was not significantly different from that of the control. However, the primary benefits for the plants included the alleviation of drought stress and the mitigation of Ca and Mg deficiencies in the tissues [124]. In a study conducted by Martins et al. (2024) in a commercial olive orchard, the authors found that the addition of zeolites in combination with mineral fertilizer improved the trees’ physiological and biochemical performance during periods of greater climate adversity. Moreover, at the soil level, zeolites increased the pH, extractable K, CEC, microbial biomass C, microbial biomass quotient, and soil enzymatic activity and reduced the extractable Cu [125]. In the same field experiment, the authors also explored the effects on olive fruits and oil composition and quality and found that zeolites improved fruit fatty acid composition and oil quality [109].

While both biochar and zeolites offer significant benefits, their application in specific contexts, such as olive orchards, requires further research to fully understand their long-term impacts on soil health, plant productivity, and overall farm sustainability.

4.3.3. Olive Mill Wastes

Olive oil production is associated with several environmental concerns, particularly due to the large quantities of olive mill wastes (OMWs) generated during oil extraction [126]. Olive pomace and olive mill wastewater (OMWW) are byproducts of the three-phase centrifugation process, which is the most commonly used extraction method [126]. This process produces approximately 1.5 m³ of waste per metric ton of olive oil, making OMWW one of the most polluting agro-industrial effluents due to its high acidity and elevated biological and chemical oxygen demand [127,128]. In contrast, the two-phase system, which is considered to be more eco-friendly, reduces OMWW production by up to 75%; instead, it generates a semi-solid residue known as two-phase pomace, which has a higher moisture content [129]. Although these residues can be environmentally harmful and phytotoxic, they are also rich in valuable compounds, including nutrients, anthocyanins, polysaccharides, and a variety of phenolic compounds [130,131,132]. It is important to note that the composition of these residues can vary depending on factors such as olive variety, harvest timing, processing techniques, and environmental conditions [133].

Given these properties, the application of OMW as a soil amendment under controlled conditions has raised increasing interest [126]. Properly applied, OMWs improve soil fertility, enhance organic matter content, increase nutrient availability, and promote microbial diversity [126,134,135]. However, improper application, such as the use of excessive amounts or poorly timed usage, can inhibit crop growth, as observed in early wheat growth studies, though no significant negative effects were noted at harvest [136].

In olive orchards, controlled applications of fresh OMWW over three consecutive years have been shown to improve soil fertility and enhance nutrient cycling, and they have proven to be cost-effective due to their high organic matter and K content [137]. Building on this, Abboud et al. (2023) found that long-term use of OMWW improved soil properties without compromising olive oil quality, supporting the safe application of 50 m³/ha every two years in semi-arid olive orchards [133]. Research by Nasini et al. (2013) demonstrated that two-phase pomace improved olive tree growth without causing long-term negative impacts on soil chemistry and microbiology [138]. Furthermore, Podgornik et al. (2022) reported that combining two-phase OMW with mineral fertilizers, such as NPK 15:15:15, enhanced soil properties due to the high organic matter content of the OMW. They also observed that calcareous soils, with their strong buffering capacity, mitigated the phytotoxic effects of two-phase pomace by accelerating the decomposition of phenolic compounds, and they recommended limiting the application to a maximum dosage of 80 m³/ha [139].

4.4. Olive Breeding

Olive cultivars represent an invaluable heritage of genetic variability, selected over thousands of years of cultivation [140]. These genetic resources are a fundamental key to climate change adaptation and mitigation, while also supporting the achievement of food security and nutrition goals [141]. Therefore, breeding programs focused on conserving and restoring genetic diversity, alongside the identification of key agronomic traits related to phenology, stress, disease resistance, yield, and oil quality, are essential to overcoming climate change challenges and preventing possible genetic erosion phenomena [141,142]. Selecting and breeding cultivars suited to high and very high orchard densities is also crucial. As reported by Rosati et al., key traits such as increased branching and smaller woody structure diameters are particularly important. These traits enhance yields by controlling excessive vegetative growth, reducing vigor, and decreasing the need for intensive pruning [143].

Recently, more than 100 olive collections have been established worldwide, with the International Olive Council creating 23 olive germplasm banks that house over 1700 well-characterized varieties [141,144]. Moreover, the need for high-performing cultivars has prompted the development of olive-breeding programs in recent years [140,145]. From an agronomic perspective, essential traits for olive breeding include early bearing, high productivity and oil content, disease tolerance, and suitability for mechanical harvesting; these are essential requirements for plant products derived from any olive breeding program [145]. Based on these criteria, several new commercial varieties have already been developed, such as “Kadesh”, “Barnea”, “Maalot”, and “Askal” in Israel [146]; “Chiquitita” in Spain [147]; and “Arno”, “Tevere”, and “Basento” in Italy [141,148].

Additionally, progress has been made in identifying genotypes potentially resistant to Xylella fastidiosa. In 2021, a study examining genetic diversity in a large collection of Mediterranean olive trees, revealed a strong genetic linkage between a Tunisian cultivar and the Italian varieties “Leccino” and “FS17”, both known for their tolerance to this bacterium [27].

Despite significant efforts over recent decades, olive breeding still lags behind that of other fruit species, such as grapevines [149]. The primary challenges in olive breeding are due to the high heterozygosity of olive trees, their large number of chromosomes (n = 23), and the complex composition of their DNA [150]. Furthermore, the extreme variability in traits affecting olive oil quality observed in progenies from cross-breeding programs further complicates breeding efforts [151]. To address these challenges and advance olive breeding, continued research and development are essential.

5. Short-Term Adaptation Strategies

5.1. Irrigation Systems

Although olive trees are considered drought-tolerant species, future climate scenarios for the Mediterranean region project yield decreases of 15–20% in groves without irrigation [49]. Irrigation requirements are also expected to rise by 18.5% due to climate change, indicating that rainfed olive cultivation may become unsustainable [16]. This suggests that rainfed olive cultivation may become increasingly unviable under future conditions. Therefore, effective irrigation management will be vital for improving the environmental and economic sustainability of both low- and high-density olive orchards.

Water-saving measures have evolved through years of technological development, with deficit irrigation (DI) emerging as a key sustainable strategy. Deficit irrigation reduces water use by supplying irrigation volumes below the crop’s full evapotranspiration (ETc) needs, allowing significant water savings without compromising production [152]. The main DI strategies include sustained deficit irrigation (SDI), where a fraction of ETc is consistently applied throughout the growing season; regulated deficit irrigation (RDI), which applies reduced irrigation only during periods when the tree can tolerate water stress; and partial root-zone drying (PRD), where irrigation alternates between different parts of the root system, keeping half in a drying state while the other half is irrigated. To ensure precise water delivery, technology to monitor soil moisture and plant water status can be used. Commonly used metrics include leaf and stem water potential, stomatal conductance, and evapotranspiration [28,153,154,155,156,157]. Furthermore, as described in other crops like almond trees, the use of spatially distributed data acquired from aerial vehicles or satellites helps create indicators, such as vegetation indices, which are widely recognized as proxies for crop water status across the orchard [158]. When selecting an irrigation strategy, it is crucial to consider the olive tree’s growth cycle and its sensitivity to water deficits. The most critical periods for water supply occur during bloom, fruit set, and the onset of fruit ripening. Olive trees are more resistant to drought during the mid-summer pit-hardening stage [157].

Several studies have shown that DI can optimize water use in olive cultivation, which, if properly tailored, can result in significant water savings without compromising tree growth or yield and even in the improvement of the olive oil quality [28,49,153,154,156,159].

For example, Arbizu-Milagro et al. (2023) found that moderate RDI (50% of ETc at pit hardening) saved 19% of water without reducing growth and yield, while precision irrigation (based on daily trunk growth) increased olive oil production by 7%, with 31% water savings. On the other hand, moderate RDI (25% of ETc at pit hardening) and SDI (50% of ETc) resulted in reduced tree growth and lower olive and oil yields compared to the control with full ETc irrigation [28]. Similarly, Ben-Gal et al. (2021) reported that RDI based on stem water potential improved both water productivity and olive oil quality compared to SDI (80% of ETc) [154]. In addition to improving drought resilience and water use efficiency, DI can enhance beneficial compounds in olives, such as polyphenols, further boosting oil quality [154,160].

In addition to optimizing irrigation levels, other studies are already addressing broader environmental concerns associated with irrigation systems. Sobreiro et al. (2023) concluded that RDI and PRD are effective DI options, and integrating DI with other sustainable practices, such as cover cropping and no-tillage, can further enhance the environmental sustainability of olive orchards [156]. In arid regions, where rainfall is scarce, the use of groundwater for agriculture often leads to increased salinity, limiting crop selection. Several studies have highlighted that alternative water sources, like low-quality or reclaimed water, provide a viable strategy for addressing water scarcity and improving the water use efficiency of the overall olive cultivation [155,161,162,163,164]. However, reclaimed water typically contains higher concentrations of ions that inhibit plant growth, requiring careful management [164]. Venella et al. (2023) demonstrated that proper treatment of reclaimed water can help reduce pressure on freshwater resources, though different olive cultivars respond variably to its use [155]. Therefore, the physiological and qualitative effects on both olive trees and olive oil need close monitoring. Research also shows that reclaimed wastewater can supply significant nutrients, such as nitrogen and potassium, reducing the need for additional fertilization. Studies confirm that nutrients provided by reclaimed wastewater should be considered in fertilization management strategies [161,164]. Olive trees have a relative tolerance to saline water, making them suitable for irrigation with low-quality or saline water [162,163]. However, it is essential to monitor salinity levels to avoid long-term soil degradation and negative impacts on production. Proper management practices, including blending reclaimed water with freshwater or periodic leaching to prevent salt buildup in the root zone, are crucial for maintaining soil health. Additionally, supplying calcium (Ca²⁺) to the irrigation water, using drip irrigation, and selecting tolerant cultivars can allow long-term irrigation with saline water without affecting olive growth and yield. Fraga et al. (2020) noted that while irrigation remains a feasible climate change adaptation strategy, water scarcity could limit its application in some Mediterranean regions [49]. Thus, alternative or complementary adaptation measures should also be explored.

While current irrigation practices have improved water use in olive cultivation, there remains significant potential for future advancements through precision decision-making methods that prioritize ecosystem conservation, water availability, and broader ecological sustainability.

5.2. Pruning Management

The primary objective of pruning is to control tree growth, particularly in terms of height, to facilitate the implementation of cultural practices [165]. However, pruning should also focus on improving light distribution within the canopy (photosynthesis-oriented pruning), increasing aeration of the foliage and promoting the development of bearing shoots [166].

The effectiveness of the pruning interventions also depends on the type of cultivation practiced in the orchard. Olive trees, particularly those grown under rainfed conditions, demonstrate high plasticity when subjected to light to moderate pruning, without significant reductions in yield. This suggests that pruning can be employed to achieve various orchard management objectives—such as implementing a specific training system, balancing vegetative growth and fruiting, reducing alternate bearing, managing canopy density, or adapting the tree to a particular harvesting method—without compromising production [165,166]. Additionally, by reducing the aerial biomass of the tree, pruning decreases the overall water demand, increases the root-to-shoot ratio, and improves the water status of the remaining foliage. This is particularly beneficial in drought-prone regions and under rainfed conditions, where water availability is a key limiting factor [165]. Conversely, heavy pruning should be avoided, as it results in a significant loss of stored energy in plant tissues and removes carbohydrate-producing parts, forcing the tree to invest resources in restoring its photosynthetic capacity [165]. Recent studies have also highlighted the benefits of summer pruning, which involves the removal of suckers from the central part of the canopy [29]. Cinosi et al. (2024) reported that summer pruning can have effects similar to irrigation, improving tree water status and physiological conditions. This practice enhances photosynthetic activity, leading to increased fruit oil content, and the derived oil is more aromatic and less bitter and spicy [29].

In high-density and super-intensive irrigated orchards, where rapid tree growth leads to dense canopies, pruning becomes essential to ensure adequate light penetration and aeration. However, orchard management must also consider the age of the orchard. In young, high-density orchards, Tombesi et al. (2014) found that unpruned trees were more productive than those subjected to pruning, as pruning removed bearing shoots. In these young hedgerow olive orchards, tree canopies do not experience reciprocal shading or lack of light penetration; so, minimal pruning should be applied and limited to removing canopy portions not harvested by overhead machines [167]. However, this productive advantage can diminish after the third year, as reported by Lodolini et al. (2019) [168]. As orchards mature, canopy volume becomes constrained by the size of the harvesting machinery and the need to manage canopy shading, making pruning necessary. Care must be taken to control tree size without disrupting the vegetative–reproductive balance, while ensuring efficient mechanical harvesting. The combination of pruning intensity, timing, and position within the canopy is crucial for managing this balance and controlling canopy size [169,170]. Research by Cherbiy-Hoffmann et al. (2012) revealed that excessive mechanical pruning can trigger vigorous vegetative growth, increasing self-shading and reducing flower differentiation, ultimately lowering fruit yield [171]. In line with this, Lodolini et al. (2019) found that heavy early spring pruning resulted in lower fruit yields than minimal early spring pruning due to significant vegetative growth and water sprout emissions [168]; in contrast, heavy late spring pruning (after full bloom) reduced vigorous re-sprouting but achieved similar yields to heavily pruned early-spring trees. It was also observed that intense winter pruning, particularly winter topping, increased vegetative re-sprouting [171,172], while summer pruning reduced it [169,172]. Excessive vegetative re-sprouting diverts resources away from productive shoots, leading to a reduction in fruit-bearing structures [168]. Lodolini et al. (2018; 2023) suggest that combining winter lateral pruning and summer topping helps maintain a good vegetative–reproductive balance (a high number of sprouts with limited vegetative vigor and high fruit production) in young trees and also leads to a more compact shape [169,170]. Thus, mechanical pruning should be performed with light to moderate intensity to avoid excessive water sprout emissions on older wood and to preserve long-term fruit production [172].

Most of the limited research on pruning management often focuses on traditional goals, the ability to influence tree architecture, light interception, and ultimately fruit yield, but its potential as a tool for mitigating the impacts of stressors like drought and heat is less thoroughly explored. There is a need for more focused studies to scrutinize how different pruning techniques—such as timing, intensity, and type—can be optimized to improve water use efficiency, reduce heat stress, and promote the overall health and longevity of olive trees in the face of changing climate conditions. By advancing our understanding of pruning in this context, we could unlock new, practical strategies that olive growers may use to adapt to and mitigate the effects of climate change.

5.3. Particle Coating Films

Particle coating films are made from aqueous formulations with inert mineral particles, creating a reflective layer once sprayed on the leaf surface. This layer helps to reflect excessive ultraviolet and infrared radiation while reducing the amount of photosynthetically active radiation that reaches the plants, protecting crops from intense sunlight and high temperatures. These films have been formulated with substances like aluminum silicates and calcium compounds, and their effectiveness has been increasingly studied [173,174,175,176,177].

Kaolin, a naturally occurring aluminum silicate (Al₂Si₂O₅(OH)₄), is one of the most well-studied and widely used materials for that purpose. According to Brito et al. (2019), kaolin’s effectiveness stems from its ability to reflect excessive radiation, preventing heat buildup on leaves and reducing water loss through transpiration [173]. This helps plants to maintain high stomatal conductance and improves overall water status. Kaolin also provides direct protection by reducing photodamage from excessive sunlight and indirect protection by lowering oxidative stress, resulting in cooler leaf temperatures and better hydration. By reducing both stomatal and non-stomatal limitations and enhancing light distribution within the canopy, kaolin boosts photosynthetic activity throughout the plant. The leaves’ hardness and carbon consumption during respiration and secondary metabolism are also reduced, leading to overall increased growth, yield, and harvest quality. Numerous studies have demonstrated the effectiveness of kaolin in various crops, including olive trees and grapevines, which have been extensively explored by our research team, under rainfed and deficit irrigation Mediterranean conditions [173,177,178,179]. In olive trees, our findings show that kaolin improves water status and photosynthetic capacity, reduces nighttime water loss, oxidative damage, and leaf sclerophyll and enhances yield and olive oil quality [173,179,180,181,182]. However, kaolin performs best under moderate stress conditions and may lose its protective capacity under prolonged severe stress; on the other hand, it can negatively affect photosynthetic capacity under non-stressful conditions [173,179,181,182,183,184].

Research on particle films from other materials is less extensive. Zeolites are crystalline aluminosilicates that have previously been addressed as soil amendments. However, they can also be applied as particle films to protect crops, reducing leaf temperature and improving water use efficiency and positively influencing yield and fruit quality [174,175]. Beyond their reflective proprieties, the effectiveness of zeolites can also be attributed to their unique structure. Zeolites consist of interconnected [SiO₄]^4‒ and [AlO₄]^5‒ tetrahedra, which create channels and cavities that hold “guest” molecules like cations and water, which are loosely bound and can be exchanged reversibly. This structure gives zeolites three important features, a high capacity for cation exchange, the ability to undergo reversible dehydration, and the ability to act as molecular sieves [175,184]. Zeolites are also believed to enhance photosynthesis by adsorbing carbon dioxide (CO₂) molecules and releasing them slowly, increasing the CO₂ concentration near the stomata [174,175]. In apple trees, zeolite application did not significantly affect growth, water uptake, or dry weight, but an initial increase in photosynthesis was observed, followed by a decrease after two weeks [174]. In Mediterranean vineyards, Valentini et al. (2021) reported that zeolite reduced berry temperatures and increased anthocyanin levels in both grapes and wine, without affecting vine gas exchange, yield, or soluble solid accumulation [30]. Petoumenou (2023) reported decreased leaf temperature, improved net photosynthesis, intrinsic water use efficiency, and yield, although it did not affect the sugar concentration or pH of the must; however, it increased total acidity and decreased total phenolic content [185]. In olive trees, Morrone et al. (2024) found no effects of natural zeolites on photosynthetic activity or olive size. However, the oil produced from treated trees showed higher phenolic content and more intense bitterness and spiciness [186]. Rotondi et al. (2021) observed no influence of zeolites on photosynthesis, stomatal conductance, transpiration, or water use efficiency in olive trees, but the oils from zeolite-treated plants had higher intensities of gustatory and olfactory secondary flavors [183]. Rotondi et al. (2022) found that olives treated with zeolite had higher oil content, and the resulting oil had higher levels of total phenols, tyrosol, and deacetoxy oleuropein aglycon. Comparatively, they concluded that zeolite particle films were more suitable for cold and humid environments, while kaolin may be preferred in other conditions [184].

Calcium-based compounds, such as calcium carbonate (CaCO₃) and calcium oxide (CaO), are white, clay-like minerals that can be sourced from renewable resources like eggshells and seashells. These compounds are also known for their reflective properties, which help reduce incident radiation [177,187,188,189]. Calcium is also crucial for regulating several essential cellular processes, including cell division and expansion. It functions as a counter ion for the transport of inorganic and organic anions across the tonoplast and serves as a key intracellular second messenger. Additionally, calcium is vital for maintaining cell wall stability by facilitating the cross-linking of pectin molecules, which directly influences cell wall integrity [190]. Research on these compounds is still limited. In olive trees in Egypt, Abd-Alhamid et al. (2019) reported that CaCO₃ increased yield in two cultivars, although it had no clear effect on oil content [191], and Hagagg et al. (2019) observed improvements in vegetative growth, leaf pigments, and mineral content [192]. In other crops, da Silva et al. (2019) found that both CaO and CaCO₃ particle films increased chlorophyll content, reduced leaf temperature, and enhanced photosynthetic capacity in American grapevines (Vitis labrusca L.) [187]. Oliveira et al. (2021) also reported improvements in photosynthetic pigments and capacity and yield in sweet potatoes with CaO application [188]. In citrus, Bernardi et al. (2023) found that leaves coated with CaCO₃ exhibited improved CO₂ assimilation, enhanced photosystem II efficiency, and lower leaf temperatures over time, which were associated with increased antioxidant enzyme activity [176].

While kaolin has been extensively studied and widely used, its effectiveness diminishes under prolonged severe stress, indicating the need for complementary practices under such conditions. Zeolites and calcium-based compounds, though promising, have seen limited research, particularly in olive cultivation. Moreover, there is a critical need to explore and discover new particle film materials, especially in regions where existing options are not readily available or are less effective due to local environmental conditions. Comprehensive studies are needed to optimize formulations, refine application methods, and understand long-term effects across diverse environmental conditions. Integrating these advancements with precision agriculture technologies could further enhance their efficacy, ensuring that particle coating films contribute meaningfully to sustainable crop production.

5.4. Exogenous Application of Plant Growth Regulators and Biostimulants

The exogenous application of plant growth regulators and biostimulants has emerged as a promising strategy to enhance the resilience of olive trees to climate change. However, their use in olive cultivation is still limited, and information about their advantages remains sparse. Some compounds gaining traction in this field include salicylic acid (SA), abscisic acid (ABA), glycine betaine (GB), proline, chitosan, seaweed, silicon (Si), and selenium (Se).

Salicylic acid is traditionally known for its role in plant defense against pathogens, but it also enhances tolerance to abiotic stresses such as drought and high temperatures [193,194]. The research conducted by our team on olive trees demonstrated the positive role of exogenous SA in drought adaptability, with an optimal concentration identified at 100 µM. The mode of action involves ROS detoxification and osmoregulation, leading to improved leaf water status and reduced photosynthetic limitations; it also involves the regulation of plant ionome and the optimization of the shoot/root ratio. SA application not only improved yield and reduced olive oil oxidation but also influenced phenolic accumulation in olives and olive oil, with variability depending on the year’s climatic conditions [179,182]. Similarly, El Refaey et al. (2022) reported that exogenous SA increased nutrient content, improved water status, and enhanced the growth, yield, and fruit quality of rainfed olive trees [31].

Abscisic acid is a well-known plant stress hormone that regulates a variety of molecular, biochemical, and physiological processes, making it a potential mediator for drought tolerance in various plants [195,196,197,198]. In young olive trees subjected to drought, ABA pre-treatment delayed the negative effects on stomatal conductance and net photosynthesis, improved turgor maintenance through osmotic adjustment, reduced drought-induced water status decline and oxidative stress, and enhanced root growth and water use efficiency. During drought recovery, ABA improved physiological and biochemical functions, thereby enhancing recovery capacity [199].

Glycine betaine and proline, as compatible solutes, help induce stress tolerance by maintaining cell turgor or osmotic balance, stabilizing the structures and functions of certain macromolecules and managing reactive oxygen species levels to prevent oxidative burst [200,201]. In drought-stressed olive trees, Denaxa et al. (2012) found that GB application improved the water status and net photosynthesis [202], and Graziani et al. (2022) also reported an enhancement of stomatal conductance and photosynthetic pigments [203]. Exogenous proline application has been shown to improve salt tolerance in young olive trees by enhancing antioxidative enzyme activities, photosynthetic activity, and overall plant growth, as well as maintaining suitable water status under salinity conditions [204,205]. Additionally, both GB and proline positively influenced olive trees exposed to lead stress, with proline providing better tolerance than GB [206].

Seaweed extracts are renewable bioresources gaining recognition for their ability to enhance plant resilience to abiotic stress. These extracts contain a variety of organic and inorganic bioactive compounds, including polysaccharides, polyphenols, phytohormones, betaines, carotenoids, minerals, lipids, and proteins. The enhanced growth effects are attributed to the synergistic activity of all the components on plant growth and functions. Although the specific mechanisms of action remain unknown, seaweed extracts exhibit phytoelicitor activity, triggering defense responses in plants and enhancing growth regulation [207,208]. Various commercial seaweed biostimulants are available, though their effectiveness can vary depending on the type of seaweed, quality, and composition of the extract, as well as the application method, concentration, and frequency [207]. For instance, Nikbakht et al. (2024) observed that injecting seaweed extract into the trunks of droughted olive trees improved proline levels, water status, and photosynthetic pigments [209]. Similarly, in salt-stressed olive trees, algae extract sprays contributed to improved growth, yield, fruit quality, and oil content [210]. Graziani et al. (2022) also reported that biostimulants based on a micro-algae and seaweed mix improved the resilience of young olive trees to drought, with distinct enhancements in photosynthetic pigments, stomatal conductance, and water status [203].

Chitosan is gaining attention as both a biostimulant and a plant protection product. Derived mainly from the shells of marine invertebrates and the wastes of the marine food processing industry, chitosan is a natural, biodegradable, and biocompatible polysaccharide with multidirectional bioactivity. Its key properties include the induction of plant defense mechanisms and the regulation of metabolic processes [211]. In olive trees under semi-arid conditions, chitosan sprays enhanced vegetative growth, leaf photosynthetic pigments, and mineral content, while also improving yield, oil yield, and fruit quality [212,213]. Other studies have shown that chitosan increased olive tree leaf area, total chlorophyll, and proline content, alongside improving fruit quality and oil properties [214].

Silicon is not considered an essential nutrient for plant growth, but its beneficial effects on stress tolerance are well documented in various crops. Si enhances stress resistance by regulating physiological processes, maintaining ionic homeostasis, and activating antioxidant systems [215,216]. In olive trees, Si foliar sprays proved beneficial for stress resistance under semi-arid conditions by improving photosynthetic pigments, water status, and reducing osmoprotectant levels and oxidative stress indicators. These benefits extended to improved growth, yield, and reduced fruit drop [217]. Si injections into olive trunks also demonstrated similar positive effects, enhancing drought stress resistance [209]. Additionally, Si has been shown to mitigate the adverse effects of salinity in olive trees by increasing antioxidative enzyme activity, enhancing root mass efficiency, reducing transpiration rates, and promoting nutrient absorption [218]. However, it was indeed observed that in non-stressful conditions, Si is not essential but can stimulate growth by promoting nutrient uptake and translocation, particularly of potassium [219], underscoring its role in stress protection.

Selenium, though not an essential nutrient for plants, plays a significant role in alleviating abiotic stress when applied exogenously. Se enhances stress tolerance by boosting antioxidant defense mechanisms, improving osmoprotectant levels, reducing cellular damage from oxidative stress, and promoting the uptake of beneficial substances. Se also modulates stress-related gene expression, contributing to better growth and productivity under adverse conditions [220]. In olive trees, Se foliar application has been shown to improve drought resistance by protecting cells from oxidative damage, regulating water status, and enhancing photosynthesis and fruit yield [221]. Additionally, Se application in olive trees under water deficiency conditions, has been linked to improved oil nutritional value, stability against oxidation, and extended shelf life [222].

Integrating these plant growth regulators and biostimulants into olive cultivation practices represents a proactive approach to managing the impacts of climate change. By enhancing the physiological and biochemical responses of olive trees to stress, these treatments can help to maintain productivity and ensure the sustainability of olive orchards in increasingly unpredictable climates. Continued research and field trials will be essential to optimize application methods and dosages, ensuring these interventions provide maximum benefits under specific environmental conditions.

While the exogenous application of these compounds offers promising avenues for the enhancement of olive tree resilience, there is a clear need for more comprehensive and long-term studies. There is an urgent need to discover and develop new sustainable bio-based products for crop protection and locally adapted solutions. Another critical area for improvement is the need to explore the synergistic effects of combining different biostimulants and plant growth regulators. The current research often isolates the effects of individual substances, but in practice, these compounds may be applied together, potentially leading to either enhanced benefits or unforeseen antagonistic interactions. The research also indicates a gap in the understanding of the economic feasibility of the widespread adoption of these treatments. While some studies demonstrate physiological benefits, the cost-effectiveness and return on investment for growers remain underexplored, particularly in regions with limited resources.

6. Conclusions and Future Perspectives

Climate projections reveal substantial challenges for olive cultivation, including altered precipitation patterns, rising temperatures, and increased frequency of extreme weather events. Additionally, olive-growing regions are particularly vulnerable to erosion and soil degradation. These factors will impact olive tree growth, fruit quality, and overall yield. Addressing these challenges will require not only the expansion of olive cultivation into new areas but also significant adjustments in management practices at the regional level. With a growing global population, achieving “zero hunger” while ensuring sustainable agriculture and food systems remains one of the foremost challenges.

This review underscores the critical intersection of climate change impacts and sustainable agricultural practices in olive cultivation, highlighting the urgent need for adaptive strategies to ensure the resilience and profitability of the olive industry in a rapidly changing climate. It provides a comprehensive overview of recent advancements in the olive sector, identifying several adaptation strategies that offer both long-term and immediate solutions. On a practical level, the findings offer valuable insights for olive growers, policymakers, and industry stakeholders by providing clear guidance on how to enhance crop resilience in the context of climate change and improve agroecosystem health. Long-term practices such as cover cropping, mulching, soil amendments (including biochar, natural zeolites, and olive mill wastes), and breeding programs show promise in enhancing soil health, improving water retention, and boosting plants’ resilience to climate stressors. Short-term strategies, including optimized irrigation systems, pruning management, particle coating films (such as kaolin, zeolites, and calcium-based products), and the exogenous application of biostimulants and plant growth regulators (like SA, ABA, GB, proline, chitosan, seaweed, silicon, and selenium), can provide immediate relief and improve plant physiological responses under adverse conditions.

However, institutional barriers may impede the acceptance and adoption of sustainable practices in olive cultivation. Issues such as land tenure security, limited access to finance, and inadequate government subsidies can hinder farmers’ ability to implement the recommended strategies. Additional challenges include complex regulatory constraints, insufficient agricultural extension services, limited market access for sustainably produced olives, and cultural resistance to change.

A key component of the advancement of these strategies is the integration of education for both farmers and policymakers about the impacts of climate change and soil degradation, as well as the best agronomic practices to mitigate these effects. This could be facilitated through living labs, workshops, and demonstrations of products and technologies by industry stakeholders, farmer associations, and research institutions.

This revision also has the potential to influence agricultural policies. Currently, it is essential to align agricultural practices with evolving environmental policies and sustainability goals, such as those outlined in the European Green Deal [223] and the Sustainable Development Goals (SDGs) [65]. Additionally, developing policies supporting farmers’ adoption of sustainable practices is crucial. Ongoing examples include the EU’s Common Agricultural Policy (CAP), which aims to ensure a stable and sustainable food supply, safeguard farmers’ incomes, protect the environment, address climate change, and support rural economies [224]. Another example is EU Regulation 2019/1009, which regulates the use of fertilizers and harmonizes the market for these products, encouraging the transition away from synthetic plant protection products [225]. Future policy frameworks must focus on incentivizing sustainable farming practices, promoting research and development of climate-resilient technologies, securing land rights, and providing financial and technical support to farmers.

On a theoretical level, by categorizing adaptation measures into long-term and short-term strategies, the study provides a comprehensive framework that enhances our understanding of how perennial crops like olive trees can build resilience against environmental pressures. This framework is adaptable to other crops and can serve as a foundation for future research in agricultural adaptation to climate change. A more critical analysis of these practices reveals the complexity of their implementation, as their effectiveness is often contingent on site-specific factors, requiring careful customization to local conditions. Moreover, some long-term practices may take years to manifest their full benefits, necessitating continuous monitoring and adjustments over time. Future research should also focus on refining irrigation technologies with the support of precise decision-making methods; optimizing pruning techniques; exploring novel particle coating materials to use in locations where others are not naturally occurring and enhancing the understanding of the current materials; and optimizing biostimulant formulations and exploring the potential synergy effects with plant growth regulators. Additionally, ongoing investigations into long-term adaptation strategies, such as cover crops, mulching, and soil amendments, will be crucial as their effects unfold over time, along with the exploration of more tailored cover crops for varying climatic conditions and other materials for mulching and soil amendments. Further interdisciplinary collaboration between agronomy, climate science, economics, and policy will be essential to develop region-specific solutions and ensure the success of climate-adaptive agriculture. Working together across these areas will provide a clearer picture of the challenges and help create holistic solutions for adaptation.

In summary, the future of olive cultivation depends on integrating adaptive sustainable practices with technological advancements to improve the sector’s environmental and economic sustainability. By continuing to explore and implement these strategies, the olive industry can better withstand climate challenges and contribute to global sustainability and food security goals. Future work should remain focused on harmonizing innovative practices with policy frameworks to drive sustainable progress in olive cultivation.