Forests are renewable natural resources that provide multiple goods and services to fulfil societal and environmental wants and needs. Efficient forest production and wise and balanced use are therefore crucial to sustain the supply of these resources. However, numerous challenges exist for efficient forest utilisation, mostly because of the resource trade-offs [1
] coupled with ongoing forest harvesting policies and practices [2
]. As one of the dominant natural forest harvesting practices, selective logging contributes nearly 15% of the global timber needs [3
] and is therefore of global concern to ensure sustainability of global forest benefits. Although only the trees that have a commercial value are removed under this approach, it is argued that insufficient attention has been paid to efficient management of selective logging practices, leading to forest degradation [6
], thereby reducing forest product supply [7
], increasing forest carbon emissions [8
] and deterioration of wildlife habitat [3
]. An assessment of these harvesting practices in a specific context is therefore important to understand their possible implications and to encourage policy makers and forest managers to act for better forest management outcomes.
The amount of forest products recovered from forest harvesting operations is one of the key indicators used to assess the socio-economic and environmental effectiveness of natural forest management. Specifically, timber volume recovery is one of the key determinants of financial attractiveness in forest management [5
]. Although the level of such effectiveness is defined according to the needs and socio-economic livelihoods of the local people and the political, environmental and market settings of a specific context [10
], optimizing societal and environmental benefits from forest products (goods and services) has been increasingly important in the context of mitigation of and adaptation to a changing climate [15
]. However, the current body of knowledge focuses largely on harvesting impacts on forest growth and tree regeneration dynamics [20
] and long-term stocks of timber, biomass and carbon [5
]. Limited attention is given to recovery rates of harvested products and carbon emissions along the timber value chain from mature forest stands [9
] in both developing and developed countries [7
]. Recent studies show increased attention being paid to logging-related forest carbon emissions from selective logging in relation to reducing emissions from deforestation and forest degradation (REDD+) perspectives [15
]. However, these are confined to a few specific examples and comparative studies between developed and developing countries are still lacking.
This paper presents the cases of Queensland Australia and the Tarai forest of Nepal, highlighting the recovery and utilization of forest products, as well as associated harvesting damages and its implications for forest-based carbon emissions under selective logging. In so doing, we aim to answer three key questions: (a) What is the forest product volume recovery and utilization percentage after tree harvest? (b) What is the average rate of damage from harvesting to neighbouring tree species? and finally (c) What are the implications of current harvesting practices for carbon stock potential of harvested wood products along the production chain? Exploration of these questions is important for the following reasons. First, the study will inform policy makers on the amount of recovered forest products and highlight the potential implications of current practices for forest-based carbon mitigation potential. For Nepal, this would be the first study of this kind and therefore fills the knowledge gap on forest product recovery along the forest production chain. For Queensland, the study will add value to quantifying the harvesting wastages in Spotted gum-dominated private forests and will contribute to addressing the issues of increased harvesting related wastage in the forests [27
Second, the assessment offers empirical evidence as to whether existing forest harvesting systems (policies and practices) need modification to respond to national and global challenges for maintaining demand for wood products as well as conserving other forest ecosystem services. Such actions will support the sustainability of wood-based industries in both countries [29
] with additional positive impacts on industry profits, carbon benefits, state revenue, and employment and income to the State and the local communities. Finally, exploration of the separate cases of forest management practices in two different economies opens up avenues to share better practices and areas of potential improvement in forest product utilisation, thereby enhancing the role of forests in climate change mitigation.
Variations in the range of DBH and the height of harvested trees in Nepal and Queensland could be due to differences in tree felling objectives. In Nepal, tree harvesting is not only for specific purposes such as supplying sawlogs, fencing poles, electricity poles as in Queensland. Since diseased, dying and decayed (3Ds) trees are the first priority in the case of selective logging in Nepal, the size of felled trees varies significantly. Further, fuelwood is important for peoples’ livelihoods and therefore, the big, straight trees are not the only targets. Since trees in Queensland were harvested for sawlogs, harvesters selected the mature, big healthy trees resulting in minimal variations in their dimensions.
Some studies have reported that the quantity of selective logging residue varies widely from one to five times the extracted timber indicating a recovery rate as low as 20% [60
]. Although the extent of residue depends on the local conditions, researchers have often estimated a ratio of 1:1, that is, a cubic meter of residue for every cubic meter of extracted logs [61
]. Table 9
summarises the findings of such studies.
Our result for Queensland (52.8%) is close to the findings of earlier studies in similar types of production forests in Australia. However, in the case of private native forests of Southeast Queensland (the current study site), Ngugi, Neldner, Ryan, Lewis, Li, Norman, and Mogilski [32
] reported sawlog biomass recovery of only 41.4%, relatively lower than our recovery result. The main reason for the relatively higher recovery rate in our study in Queensland could be the selection of the specific species (Spotted gum) for sawlogs. Harvesters have selected the healthiest and straightest trees and left trees with minimum recovery potential untouched.
Some of the key reasons behind the significant difference in the product recovery rate in Nepal (94.5%) and Queensland (52.8%) could be: (i) differences in livelihood dependency on forest resources, (ii) market demand/standards and maturity in the marketing systems, (iii) costs associated with harvesting and processing, and (iv) royalty systems. Since fuelwood is the key source of energy for the majority of the Nepalese population [70
], utilisation of small stems and the branches supports increased recovery of forest products with negligible wastage on the ground. Likewise, communities use small wood as supporting materials for growing vegetables and other agricultural products on their farm. In contrast, the market and its standards play a dominant role in Queensland. Since the timber market in Queensland is well developed and driven by specific standards, only the commercially saleable logs with particular market requirement (for example: straight bole, round cross section, minimal defects and standard length-minimum of 2.4 m with consecutive differences of 30 cm after that) are harvested [32
]. This system is well-tailored to market demand and harvesting operations, exerting a direct impact on recovery rate and product maximization [72
]. Moreover, value chain actors are well coordinated and play a key role in policy formulation and in driving practices on the ground [73
]. In addition, timber-harvesting operations including transportation, processing and handling costs are much costlier in Queensland than in Nepal. The increased labour cost has been a significant issue influencing the overall timber production chain and recovery. Trees and logs with even minimal defects and minimum deviation in length beyond specific sizes are left on the forest floor because of the costs of handling and transportation. Finally, the royalty system in Queensland is more general and is the same for all hardwoods, not differentiating royalties paid for particular species. However, in Nepal a royalty system is different between species and therefore it has encouraged harvesters to maximize the product volume recovery.
Despite the fact that intensive whole tree harvesting, that is, stem plus harvesting residues, may have long term negative effects on soil fertility, tree growth and ecosystem functioning [74
], optimisation of forest product recovery and utilization is equally important to incentivize the forest owners from an economic point of view and hence needs balanced strategies. The key concern is that the current amount of residues left in Queensland’s forests is even more than the quantity of biomass required maintaining environmental functioning of the forests. Ngugi, Neldner, Ryan, Lewis, Li, Norman and Mogilski [32
] commented that current harvesting practices in Queensland’s native forests have left 22.6% of the additional commercially potential biomass even if we consider retaining 36% of the biomass on the forest floor is necessary for environmental purposes. Our results also support earlier studies [28
] which found that the current amount of forest product recovery from private native forests in Queensland is lower than the optimum level. At the same time, there are significant opportunities for utilizing small wood products for the purpose of pulp, paper, small sized veneer or other bioenergy purposes. Prospects for utilizing forest residue as a source of biomass and bioenergy are being discussed in Australia, including Queensland [28
], but are yet to materialize in policies and practices.
Extraction of 73.3% of total woody biomass from the forest indicates a greater potential for carbon to be locked in HWPs in the long run in Nepal. However, nearly 15% of the extracted biomass was used as fuelwood, leading to direct carbon loss within a year or two. Even within that scenario, 44.1% of the total estimated carbon in extracted products remains on the logs in Nepal compared to 32.3% in Queensland. Nearly a five times higher amount of carbon mass was left in the forests (per cubic meter of extracted timber volume) of Queensland compared to Nepal implying that the current policies and practices need attention to explore options to optimize utilization of harvested wood products and consideration of their role in carbon mitigation benefits.
Our findings indicate that the difference in sawn-wood recovery between the countries studied might be due to local practices, to different utilisation purposes, as well as to policies and standards. Sawn wood recovery after saw-milling varies with access to and use of sawing technology, the final products to be produced, local practices of using wood products and the quality of species [28
]. Sawn wood recovery of Queensland’s hardwood species was found to be slightly lower than the national average for Australia of 40.2% [43
]. Likewise, compared to the theoretical average sawn wood recovery of 42% to 50% in general [61
] and average sawmill recovery rates of 50.8% in developing countries [77
], our result in Nepal is slightly higher and in Queensland it is lower. Since the final products of the hardwood sawlogs are used primarily for building construction purposes in both countries, use of the products is guided by building codes and standards. For example, in Nepal, the size and quality of logs are relatively flexible due to the variation in size of wooden frames used in building construction compared to Queensland where building codes and standards are more specific and strict.
Likewise, carbon in harvested products is determined by the amount of residues after round wood log processing in a sawmill. We found that, 61% of the total log carbon in Nepal and 36.3% of the total log carbon in Queensland has the potential to be locked up for another 46 years [40
]. Carbon stock in sawmill residues is considered to be the complete emissions due to the lack of exact data on the percentage of landfill and short-term uses of those residues. In this scenario, nearly 64% of the log carbon in Queensland and nearly 40% of the log carbon in Nepal will be emitted. However, discussions with sawmill owners and timber users reflect that such residues (mainly the chips and wood dust) are being used for gardens and vegetable farming as well as for animal husbandry.
Damage caused by logging is one of the key determinants of carbon emissions in logging operations and future recovery of harvested sites [78
]. The overall logging damage to plant species in our studies was lower (5 and 3.4 plants damaged for each tree harvested in Nepal and Queensland respectively), compared to earlier studies that reported damage to 20 trees in Brazil [79
], 11 trees in Gabon [55
] and 7 trees in Congo [80
]. The highest figure for damage to seedlings and saplings in these sites is associated with a higher level of regeneration in the harvested area. Nepal had an average of 21,649 seedlings and 1662 saplings per ha [31
] whereas Queensland Spotted gum-dominated native forests hosted up to 2500 regenerating stems per ha [81
]. The larger trees and minimum regeneration supported minimal damage to the undergrowth and neighbouring trees [53
], whereas in Nepal, the reverse applied with higher regeneration and wider variance in harvested tree size (28–56 cm in DBH and 8–30 m in height). In addition to the amount of regeneration per ha, the higher rate of per tree damage to seedlings, saplings and poles in Nepal compared to Queensland could be attributed to a number of other factors including topography, harvesting techniques such as reduced impact logging—(RIL), and the skills and knowledge of harvesting operators. Harvesters/labourers in Nepal were relatively less aware of harvesting techniques compared to those in Queensland. Nepalese harvesters were working as seasonal labourers rather professional tree harvesters and were not trained in harvesting operations. In contrast, Queensland’s harvesters were well aware of the techniques of directional felling and damage minimization and had been engaged in the profession for the last 15 years.
Our results relating to total emission factors in Nepal (0.488 Mg C m−3
) and Queensland (1.099 Mg C m−3
) are lower than those reported for the countries listed below (Table 10
). However, Queensland’s total emission factors are higher than those in the Republic of Congo (0.99 Mg C m−3
]. If we compare individual emission factors, we should find possible reasons behind the lower total emissions in our study. Extracted log emissions (ELE) and logging infrastructure emissions (LIF) play a critical role in lowering the emissions rate.
All the above studies measured the total extracted biomass as the committed emissions, but we considered the carbon stock contribution of harvested wood products in the long run and therefore the extracted log emissions (ELE) were relatively lower in our study. In addition, compared to the earlier studies that reported 0.24 to 0.98 Mg C m−3
], LIF in our case study sites was negligible (0.141 and 0.097 Mg C m−3
in Nepal and Queensland, respectively). This may be attributed to the specific field situation and level of mechanization on our sites. In Nepal, forest harvesting blocks were relatively smaller and were very close to the highway, so did not require many skidding trails or hauling roads. Further, a common logging deck was built and utilized for several harvesting blocks and therefore we shared the proportionate contribution of that deck for our sampled block. More precisely, harvesters used manual labour and small tractors to transport the harvested products with minimal infrastructure required. Likewise, in the case of Queensland, harvesters did not construct a separate harvesting deck as logs were piled on the open land adjacent to the forest on the same property, thus minimizing the LIF related emissions.
Emissions related to unextracted wood and incidental damage (LDF) (0.201 and 0.785 Mg C m−3
in Nepal and Queensland respectively) were relatively lower in the case of Nepal but within the range (0.50 and 1.23 Mg C m−3
) of global studies in the case of Queensland. Similar to the findings of other studies [15
], LDF has dominated the proportion of total emissions in both countries (38.8% in Nepal and 71.4% in Queensland). However, the proportion of emissions varies significantly between these two sites. The reason can primarily be attributed to the rate of forest product recovery. Higher amounts of forest residues on the ground in Queensland became the key determinant of this proportion.
Potential Implications on Sustainable Forest Management and REDD+
In line with the second commitment period of the Kyoto Protocol, the Paris Agreement in 2016 allowed accounting of HWPs carbon locked into different products based on the half-life of their end uses [51
]. Moreover, scholars have suggested extending the idea of enhancing carbon stock from sustainable forest management activities to maximizing wood product extraction and utilisation [60
]. Since the rate of forest product recovery along the wood production chain guides the level of carbon flux from selective logging operations, our findings will positively contribute to the manifestation of forest-based emission reduction initiatives such as REDD+ in Nepal and the emissions reduction fund (ERF) in Australia.
Our study reiterates that there is a huge potential to increase the forest product recovery rate in Queensland that not only contributes to the transfers and stocks of carbon in harvested products but also supports increased income, employment and sustainability of forest-based industries [32
]. The harvesting related carbon is context-dependent, including the harvesting regime and the fate of ultimate wood products. Therefore, changes in the existing pattern of HWP recovery and use will have a significant impact on the carbon balance of Queensland’s private native forests. Revision of royalty rates for hardwood species and incentives to utilise small woods and biomass for bioenergy will help to improve the recovery rate in Queensland. Further, offering incentives to the sawmill owners, harvesters and farmers under the activities of the emission reduction fund (ERF) will enhance carbon lock-up in different forms of harvested products. In addition, demonstrations of existing potential through increased recovery and use of the forest residues support a lowering of the risks of forest fire and associated damage at the local level. More importantly, increased wood product recovery has the potential for carbon mitigation by substitution impacts for building materials as well as the production of pulp and paper [27
]. For example, using logs as wooden electricity poles helps to reduce greenhouse gas emissions by a further 30% compared to using them as sawlogs [27
Realizing this potential in policies and practices may also help to replace the importation of pulp and paper primarily from Southeast Asia that is increasingly impacted by increased forest degradation [27
] and will eventually support mitigation of emissions on a global scale. Overall, the results of this study imply that increasing the recovery rate and utilizing biomass and bioenergy of wood residue will enhance the outcome of GHG benefits at least in Queensland, Australia.
For Nepal, our results have opened up an avenue for discussions on the trajectory of forest product biomass and carbon along the timber production chain. Primarily, the findings will help to estimate more accurately the actual logging related emissions as well as carbon stock in harvested wood products. These findings will be most relevant in the context where the country is in the process of implementing the Emission Reduction Program Document (ERPD) approved by the World Bank’s Forest Carbon Partnership Facility [83
]. Because the sustainable management of community-based forests in the Tarai is the core objective of this document, our study provides a sound basis for identifying monetary and non-monetary carbon benefits to the state and the communities and sets the scene for materializing REDD+ processes. As highlighted in the results, the amount of carbon stocked in harvested wood products and the minimum level of logging emissions in harvesting processes could provide evidence to negotiate for the financial incentives through REDD+ initiatives. These will ultimately support communities who have proven themselves as the real forest stewards in sustainable management of forests. However, further detailed studies with rigorous sampling could help to identify and validate the product recovery and carbon flow in all of the forests of Tarai, especially with the use of the carbon-friendly harvesting techniques the country has had in place for many years.