Introduction

The need for adaptation to climate change is an emerging focus of international policy [1]. The impacts of climate change are already being felt from the tropics (e.g., small island states, coral reefs) to the arctic (e.g., first nations communities) [2]. New international funding is being mobilized to meet these new challenges, but the committed funds are still likely an order of magnitude less than the medium-term needs [3]. As a result, recently committed funding needs to be prioritized to areas with exceptional need and/or the potential for impact in multiple sectors simultaneously [4].

Ecosystem-based Adaptation is the use of ecosystem services to help people adapt to climate change. Intact ecosystems provide clean water, shoreline protection, and other services in the face of climate change, providing adaptation options that are often cheaper and more enduring than technical or engineering solutions [5]. Maintaining intact ecosystems benefits both human adaptation to climate change and biodiversity. Understanding linkages between sectors is an important first step toward realizing these benefits.

Priorities linking ecosystems and food production are particularly important because human and natural responses to climate change are interwoven [6–8]. Impoverished farmers are likely to use diverse livelihood strategies that include diverse natural ecosystems and agro-ecosystems [9], and that benefit from a range of ecosystem services [10,11]. Individual species’ range shifts can break up plant and animal communities, altering ecosystem services critical to agriculture, such as watershed protection [12]. Decline in agricultural productivity due to climate change can lead to crop expansion into nearby natural habitats as farmers attempt to compensate for lost yield by increasing area under production. This may result in biodiversity loss, as well as undermining the very ecosystem services that support agriculture [13]. Understanding of these inter-dependencies under climate change is emerging [14–16]. Subsistence farmers most sensitive to climate change are in the tropics [16,17], as are the species most sensitive to climate change [14,18,19]. Critical areas in which the axes of agricultural and ecosystem responses to climate change intersect are beginning to be documented for individual regions [10,20].

Adaptation action in these areas could simultaneously enhance food security and maintain ecosystem function. This has policy relevance on multiple levels, as food security and ecosystem integrity are two of the three major benchmarks for climate change response established in the United Nations Framework Convention on Climate Change (UNFCCC), and make substantial contribution towards sustainable development, thus helping meet all three UNFCCC criteria [21]. However, studies examining the interlinkage of agriculture and ecosystem change on a global scale are lacking.

Here we model changes in food production and biodiversity to find areas in which adaptation needs are high in both sectors. Our models focus on 1) rainfed agriculture which supports many of the world’s poorest farmers [22] and 2) restricted-range bird species (i.e., historical range <50,000 km²) which are indicative of highly complex and biodiverse ecosystems [23,24]. We find multiple areas in which declining crop productivity and shifts in restricted-range species coexist, indicating possible synergies between ecosystem health and human well-being. We suggest that these areas are a valuable initial set of priorities for research and action in climate change adaptation.

Materials and Methods

Results

Ten global priority areas for adaptation funding can be identified based on intersection of changes in agricultural suitability and climatic suitability for restricted-range species (Figure 1). The ten areas comprise 9.3% of the world’s habitable lands and 10.6% of remaining natural habitats; 7-9% of the world’s poor inhabit these areas and all of the areas intersect global biodiversity hotspots (Table 2). The agricultural and ecological changes that define these areas include declines in rainfed agricultural suitability encompassing 8.9% of the world’s arable land and 12.8% of currently cultivated land in the tropics and 69% of all modeled restricted-range bird species. Investment in these areas of intersecting suitability decline can help address the intertwined adaptation needs of agriculture and biodiversity.

Download:

• PPT
  PowerPoint slide
• PNG
  larger image
• TIFF
  original image

Figure 1. Global and regional priorities for adaptation of agriculture and biodiversity in the face of climate change.

Global priorities (solid outlines) are areas of overlapping or contiguous agricultural and ecosystem change that appear by mid-century (2050). Regional priorities (broken circles) are areas of agricultural and ecological change that are less extensive and appear only later in the century (2090 scenarios). These global and regional priorities illustrated here are superimposed on a base map of 2090 A2 changes in both crops and restricted-range birds. Areas in which overall decreases are anticipated in crop suitability are shown in green, with increasing color intensity indicating multiple GCM agreement. Areas of declining climatic suitability for restricted-range birds are shown in blue, with increasing color intensity indicating multiple GCM agreement. Overlap of declining crop suitability and declining restricted-range bird climatic suitability is shown in shades of yellow (lowest GCM agreement) to red (highest GCM agreement).

https://doi.org/10.1371/journal.pone.0072590.g001

An additional seven regional priority areas harbor both agricultural and natural change that is less certain (i.e. less GCM agreement) than in the ten global priorities and therefore represent research priorities for more detailed regional analysis. These areas are Northwest Mexico, West Africa, the Cross River region, the Western Himalayas, the Eastern Himalayas, Sulawesi, and New Guinea. Most of these areas experience upper quartile crop loss or habitat suitability loss under most GCM scenarios, but with little inter-GCM agreement on areas of overlap.

The analyses used to derive these priorities are robust to alternative analytical methods, climate scenarios and climate models. The ensemble histogram approach used here (see Figures S1-S6) [43] presents the degree of agreement across multiple GCMs. The orange-red color ramp in Figure 1 indicates areas in which combined crop and ecosystem adaptation priorities are found in all five GCM results (red) through decreasing GCM agreement to combined crop and ecosystem priority found in only one GCM result (yellow). GCM agreement on non-overlapping agricultural and ecosystem adaptation priorities are shown in color ramps of green (crop loss) and blue (species range loss). This histogram approach highlights priorities that emerge repeatedly across multiple climate models, and are thus more robust to GCM uncertainty [43]. This ensemble histogram [43], in which GCM agreement is explicitly represented, contrasts with the ensemble mean approach in which the average of GCM results is taken. The ensemble histogram maintains relationships between climatic variables within individual GCMs, allowing representation of variable interactions that might be lost in an ensemble mean, for instance between temperature and precipitation in determining soil moisture. We have tested the ensemble histogram against ensemble mean approaches (Figures S4 and S5), and found that ensemble mean priorities are a subset of those determined using ensemble histograms. The priorities in Central and South America are robust across both methods, while the ensemble mean shows few priorities in Africa or Asia at the thresholds used here.

Uncertainty associated with species and agricultural modeling is more difficult to constrain. In the tropics, species ranges may not sample all climatic conditions that are physiologically tolerable, resulting in over-estimation of range loss. Adaptation priorities for non-avian restricted-range species may not match those for birds, due to different taxonomic climatic tolerances. SDM are fitted to empirical data using current climatic conditions and may not simulate future range changes well when future climatic conditions are outside the range of current climate. Adaptation in agriculture may moderate crop losses, resulting in over-estimation of crop impacts. For instance, consumption may switch to crops which may be grown in a region but are not culturally favored, once suitability for preferred crops declines. For these reasons, regional analyses incorporating social factors, taxa other than birds, and analyses of adaptation capacity are essential complements to this global analysis.

Discussion

The priorities identified here reinforce and expand on the findings of other research into agricultural and biodiversity responses to climate change. Areas of agricultural vulnerability identified in this study overlap with those defined in other global assessments of agricultural impacts of climate change [44–46]. For instance, the Indian sub-continent emerges as an area of agricultural decline in both our results and in those of other studies [22,46]. Ecologically vulnerable areas identified in our restricted-range bird modeling are broadly consistent with impacts projected in several recent studies [47–49].

Possible adaptation responses in these priority areas might include actions that integrate adaptation for agriculture and ecosystems. For instance, agroforestry can help reduce soil temperatures and maintain soil moisture as air temperatures increase, and, with the appropriate choice of tree species, can help provide habitat for restricted-range birds and other wildlife. Protecting upland forests that provide fog interception or provide watershed protection for dams may be critical for agriculture in areas of declining precipitation, at the same time providing habitats that will permit range migrations in forest birds responding to climate change. Many of these solutions require planning on scales broader than individual farms or protected areas, which is why we have aggregated our results at spatial scales roughly coincident with scales of ecosystem and regional planning (one degree).

It is likely that finer-grained analyses will confirm some or all of the regional priority areas identified (dashed outlines, Figure 1) as regions of considerable change in both agriculture and ecosystems. For instance, in this study, the island of New Guinea (Indonesian Papua and Papua New Guinea) showed high change in restricted-range birds but little agricultural change. However, this region has very limited agricultural data because the subsistence crops prevalent there are poorly captured in global agricultural records. It is likely that improved agricultural data would reveal high adaptation needs in agriculture in this area, making it a joint priority for both human and natural adaptation.

The global adaptation priorities defined here have important policy relevance. First, they highlight areas in which it is most critical to address cross-sector inter-dependencies to achieve lasting adaptation results. Second, they illustrate a broader set of solutions to planning problems that must balance short-term human adaptation needs with long-term ecological sustainability. Finally, they help guide investment toward regions that may serve as tests for planning and adaptation solutions that can evolve to help other regions simultaneously meet multiple objectives of international agreements.

The UNFCCC holds as its goal the prevention of dangerous anthropogenic interference in the climate system, “within a time-frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner” [21,50]. Our results show that food production and ecosystem integrity are jointly vulnerable in ten world regions. Because global political progress on climate change mitigation is evolving slowly at present [51], it is probable that adaptation actions in these regions will be the only means of averting the kind of damage to human and natural systems that the world has committed to avoid in the climate convention.

Adaptation investments in these regions will, at the same time, realize progress towards achieving Millennium Development Goals and the goals of the Convention on Biological Diversity. The global and regional adaptation priority regions combined hold over 10% of the world population living in poverty, typically at less than half of the global average Human Development Index (Table 2). Targeting these areas can help meet the need for global adaptation funding priorities, as well as address poverty alleviation. The biodiversity in these areas is of global importance, as all are recognized in one or more global conservation priority ranking systems (e.g., hotspots, Global 200 ecoregions – see Table 2). Investment in these areas can help pioneer demonstrations that human development and ecological sustainability are intertwined - even more intimately than at present - as climate changes.

Designing adaptation investment strategies to meet these cross-sectoral goals requires decisions at multiple scales. This analysis provides a first set of global investment priorities. At the local scale, investments that capitalize on these opportunities may come through land sharing, in which case single investments can address both priorities, or through land sparing, in which case separate investments (each with strong links to the other sector) will be required. Both approaches can be effective [52], so wise investment requires sufficient understanding of local social and biological circumstances to know which will be most effective.

Adaptation practice is currently being pioneered in first-generation projects around the world. These efforts are addressing the adaptation needs of communities and ecosystems, increasingly recognizing deep interdependencies between the two. Meeting short-term development needs while establishing long-term sustainability of ecosystem services is a fundamental challenge. Among the best places to build experience in melding human and ecosystem responses will be regions experiencing substantial change in both. Innovative solutions and lessons from these areas can inform second-generation adaptation responses worldwide. Investment in the priority regions identified here is therefore a first step in developing a lasting, multi-sector approach to adaptation.

Supporting Information

Acknowledgments

We are grateful to Guy Midgley for help and encouragement in the design of the early stages of this project. We thank the many individuals and organizations who contribute to BirdLife’s Red List assessments, including provision of point localities used in the analysis. For helpful comments on an earlier draft we thank M. Heath and E. Perry.