1. Introduction
Considerable changes in climate variables relevant to agriculture and the environment have already occurred and have been documented [
1,
2,
3]. For the agricultural portion of the Canadian Prairie Provinces, where this study was conducted, these agro-climatic changes include longer growing seasons, more crop heat units, decreasing snow-cover area, changes in precipitation from snow to rain during winter months, and warmer winters. Future changes for the prairie agricultural region indicate continued and perhaps accelerated trends in these variables and many others [
1,
4]. An increase in climate extremes, including droughts, excess moisture, and heat waves is expected for the Canadian Prairies [
5,
6]. These extremes can often have adverse effects on the environmental sustainability of agriculture. More recent work also confirms that future drought characteristics (frequency of droughts, duration, and intensity) show increases over the southern prairies [
7]. Increases in such extremes would have adverse effects on the environmental sustainability of agriculture. The effects of droughts and excessive moisture on environmental sustainability are of special concern, and are the subject of this paper.
Agriculture is an important part of the economy of the Canadian Prairie Provinces of Alberta, Saskatchewan, and Manitoba. The agriculture and agri-food system of these provinces consists of several industries including primary agriculture, farm input and service providers, food and beverage processing, food distribution, as well as retail, wholesale, and food service industries. In Canada, this sector contributed CAD
$108 billion (or 6.6% of Canadian gross domestic product) and employed 2.3 million workers [
8]. Much of this production activity occurs in the Prairie Provinces. Primary production is a key part of this system as it affects the other components of the regional economy [
9].
Although agriculture is important to the economy, environmental impacts must also be considered for achieving sustainability. Agriculture has many effects on the environment and these effects determine the environmental sustainability. Environmental sustainability is defined as sustainability of ecological services that are provided by the ecosystems [
10]. Humans depend upon these services directly or indirectly. A strong environmental sustainability would label any practice unsustainable if the natural ecosystems are put to alternative uses, such as conversion of forest ecosystems to agricultural ecosystems. A more practical definition of environmental sustainability requires that those ecosystems and ecosystem services that are essential to humans be conserved to the point of a minimum safe standard. Examples of effects include those on soil and air quality by the use of different tillage and cropping systems, and those on water quality related to the use of fertilizer and pesticides. Climate trends and extremes are expected to affect air, land, and water resources, and knowledge of these effects are crucial to achieving sustainable agricultural production and food and water security. The effects of excess moisture and drought are especially important, as they can have more pronounced impacts on the environmental sustainability of agriculture than gradual increases in temperature. For example, droughts reduce the protection of soil moisture and vegetation, and erosion can result. Excess moisture and flooding can result in water run-off leading to erosion of soil and damage to vegetative cover that protects the soil. Flooding can also damage the storage areas of fertilizer, manure, and pesticides, releasing them as contaminants into the environment. In this paper, we explore the effects of climate change on the environmental sustainability of agricultural systems, with emphasis on the extreme events of droughts and excess moisture. Therefore, our main objective is specifically to assess the effects of future drought and excess moisture on selected agri-environmental indicators. No other investigations have addressed this topic, to our knowledge.
By 1999, the member countries of the Organization for Economic Cooperation and Development (OECD), including Canada, noted that establishing a key set of agri-environmental indicators (AEIs) that could be useful for member countries was important [
11]. In Canada, Agriculture and Agri-Food Canada (AAFC) reports on a set of science-based AEIs using mathematical models showing the interactions between agriculture and the environment [
9,
12]. These two reports are the latest in the series of Canada’s agri-environmental reporting. Therefore, they are the basis for the AEIs we have selected for use, as well as associated trend information. This reporting series and their AEIs are not intended for use with climate change scenarios, but their use may be for strategic adaptation to drought and excess moisture.
Wall and Smit [
13] noted that agricultural sustainability and climate change adaptation strategies support one another and that ecosystem integrity is needed for sustaining agricultural production. However, Wheaton et al. [
14,
15,
16] were the first, according to the authors’ knowledge, to assess the possible changes in agricultural sustainability (using AEIs) as expected under climate change, and this study builds upon and expands that work. They found several of the AEIs to be sensitive to climate change and reported a possible decline in the performance of AEIs with climate change for soil erosion, contamination, soil salinization, and water quality categories.
2. Data and Methods
Environmental sustainability indicators of agriculture considered here were based on changes in the set of science-based AEIs developed by Agriculture and Agri-Food Canada [
9,
12]. The AEIs report agri-environmental performance under four main categories: soil quality, water quality, air quality, and farmland management. Each category has set of indicators addressing sub-themes within the category (e.g., from the soil health theme, sub-indices include soil erosion, soil organic matter, trace elements, and salinity). Many of the indicators can be integrated within climate change studies either directly or indirectly. Directly, these indices can be calculated using climate change scenario data and compared with values obtained under the observed climate record.
Our study methods included literature reviews, development of a conceptual framework, examination of the possible relationships, sensitivities and responses of selected AEIs to climate by examining their mathematical structures. These approaches were used to suggest possible directions of future trends in AEIs with increases of drought and excess moisture under continued climate change. In the remaining sections, the selected AEIs are described, along with an assessment of their future status.
The AEIs selected for this study were those for the soil quality, water quality, and farmland management themes. We added two more indicator types because of their relevance, one for desertification and another for water supply and demand. AEIs were selected for their utility in assessing the possible effects of current and future drought and excess moisture. We examined the mathematical models (factors affecting the relationship among stimulus that causes a change in the AEI level) of each AEI as the first step in choosing them [
15]. The AEIs that contain climate variables in their mathematical models are the most clearly sensitive to climate, and therefore either are directly driven by and may have strong relationships with climate change. We determined the nature of the relationships by the types of climate variables used (e.g., temperature, precipitation) in the indicator and whether the relationship with climate was linear or more complex and direct or inverse. Some AEIs for the category of soil quality are good candidates for exploring the direct effects of drought and excess moisture on the environment. Examples include the wind and water erosion, salinity, and particulate emission models as they include climate variables. Where it was not possible to assess indices due to a lack of direct use of climate variables in the models, climatic effects were indirectly implied from ecosystem assessments of changes in vegetation, insects, and diseases, for example.
Although drought and excess moisture affect most aspects of environmental sustainability, we focused on AEI categories and their indicators for soil quality, water quality, farmland management, and water supply and demand, as guided by our conceptual framework (
Figure 1), expertise and available literature. From the conceptual framework, we analyzed how the four AEI themes would be affected by changing climate extremes starting with the knowledge of the main characteristics of future possible drought and excess moisture events, as summarized from the literature.
Drought and excess moisture events are expected to become more common in the future on the Canadian Prairies [
5,
7]. The frequency, intensity, and extent of moderate to extreme droughts are projected to increase. At the other extreme, the review also found agreement that the frequency of severe storms and unusually wet periods is also projected to increase, leading to the conclusion that wet times will become wetter and dry times will become drier, with several driving forces supporting this finding.
Regarding drought, four main characteristics of future possible droughts in the Canadian Prairies were found: (1) increased intensity of dryness, driven by increased evaporation potential with higher temperatures and longer warm seasons; (2) droughts of 6–10 months and longer become more frequent by the 2050s; (3) the frequency of long duration droughts of five years and longer more than doubles in the future to 2100; and (4) decade-long and longer droughts increase by triple in frequency to 2100 [
5,
6]. The finding of future possible increase in droughts is confirmed by other work that finds increases in drought characteristics in the Canadian Prairie Provinces, especially over the southern study region [
7].
Shifting of climate zones poleward with higher temperatures also indicates the occurrence of drought in areas farther north of their usual positions in the study area. Worst-case scenarios should also be considered because of the severe and multiple effects of droughts. Mega droughts have occurred in the past in the Canadian Prairies [
17], and it is therefore expected that droughts will be pushed to greater severity with climate warming.
In the context of future trends in the AEIs, it is important to ask: what are the future projections of extreme precipitation events and associated excessive moisture conditions? The IPCC (Intergovernmental Panel on Climate Change) [
18] has reported on managing the risks of extreme climate events globally. The report indicates that the frequency of heavy precipitation will increase in the 21st century over many parts of the world. They gave this projection a 66–100% chance of occurring and found that this trend is particularly the case in the high latitudes.
The Canadian Prairie agricultural area has experienced extremely wet conditions in the past and these are projected to increase. Saskatchewan holds Canada’s record wettest hour under the current climatic conditions when 250 mm rainfall occurred at Buffalo Gap in the south central area [
19]. The largest area eight-hour event in the Canadian Prairies was the rainstorm of 3 July 2000 around Vanguard in southwest Saskatchewan. This storm brought about 375 mm of rainfall, exceeding the average annual precipitation of 360 mm, and caused severe flooding [
20]. The projected changes to precipitation amounts in Canada for 2041–2070 show an increase in maximum precipitation in the range of about 10–20% for the prairies for the 20-year return period of one-day precipitation [
21]. This means an increase from 40–60 mm (1941–1970) to 48–72 mm for the 20% increase.
Although the work of [
17] for the prairies focused on droughts, the climate indices (i.e., Palmer Drought Severity Index and Standardized Precipitation Index) over the future period to 2100 show some very high values, indicating wet periods for a range of Global Climate Model results. For example, some of the future wet periods appear to be as excessive as the wet period of the 1970s. The review of future possible extremes suggested that the overall prairie climate would become drier, but with substantial year-to-year variability, including an increased chance of heavy precipitation and very wet periods [
5,
6]. The next section provides an assessment of the possible changes in AEIs with projected increases in drought and excess moisture.
4. Discussion and Conclusions
This paper was an attempt to explore the possible effects of future drought and excess moisture on the environmental sustainability of agriculture. Methods included examining the possible relationships and responses of AEIs to climate drought and excess moisture using the conceptual framework of
Figure 1, by evaluating the relationship of AEI models with climate variables, and by using literature reviews. These approaches were used to suggest possible directions of future trends in AEIs with increased drought and excess moisture. The AEIs assessed were those for soil and water quality, and farmland management as developed by Agriculture and Agri-Food Canada [
9], with additions of water supply and demand categories.
The estimation of any future occurrence is difficult with many limitations because of several unknowns. However, the projections using several different methods, including climate indices, climate models, and emission scenarios provide strong agreement of the findings of increased intensity and frequency of both future droughts and extreme precipitation (e.g., [
6,
7,
17]). Measuring, monitoring, modeling, projecting, and communicating the characteristics of wet and dry climate extremes are becoming even more critical as the climate shifts and becomes less stable. Sufficient information is needed to guide planning for and implementation of effective actions to adapt to the impacts of climate extremes.
The critical issues of the effects of climate extremes on environmental sustainability of agriculture include effects on natural resources and their ecosystems, including soil quality, water quality, and water supply and demand. Results indicated the nature of future possible changes in AEIs as affected by trends in climate change and extremes. In order to meet the goal of environmental sustainability of agriculture, climate trends and extremes need to be carefully considered. Much better use of climate information and services are required to meet the goal of environmental sustainability of agriculture. The lack of consideration of climate change reduces the capability to adapt and increases vulnerability.
The possible future effects of climate change extremes examined here are conceptual, but are plausible based on the current data from climate science. Actual results may be lower, but they also might be much higher in terms of worst-case scenarios. Solutions for effects of climate extremes should also considered, especially those with the most serious consequences.
Soil quality, as measured by AEIs in the agricultural region of the Prairie Provinces, has showed an improving trend for the 1981–2011 period [
12]. However, these AEIs have strong land management drivers, and the effects of climate trends and extremes are not clear. Results regarding the effects of climate change indicate possible declining performances for soil erosion, salinization, and desertification. Results regarding the effects of climate change for other soil AEIs such as soil organic carbon, contamination by trace elements, and farmland management have even less information. All of these AEIs require more work to fully assess the effects of climate change, especially extremes, such as drought and excessive moisture.
The AEIs are numerous with four main categories containing several indicators apiece as described in [
12]. Therefore, many could not be addressed here, including air quality and biodiversity indicators. Alternatively, a critical indicator, that of water supply and demand, is not a part of the AEI indicator series by Agriculture and Agri-Food Canada [
9,
12]. However, water supply and demand was discussed here as a possible indicator, and we recommend it to be included in the AEI series. Next steps in the AEI assessments are recommended to include additional indicators and their relationships with climate change.
Results indicate that the performance of several indicators would likely decrease in a warming climate with more extremes of droughts and extreme moisture. These indicators include risks of soil erosion, soil salinization, water quality and quantity, and soil contamination. Thresholds of climate extremes, however, may be reached and result in accelerated negative performances of such indicators. The impacts of climate change are more difficult to assess for several indicators because of the effect of other factors, such as land management. AEIs are important tools to measure climate impacts on environmental sustainability of agriculture. They also indicate the success of adaptation measures and of required policy development. The climate change risks to environmental sustainability of agriculture require much more attention.