Irrigation as climate-change adaptation in the Cerrado biome of Brazil evaluated with new quantitative methods, socio-economic analysis, and scenario models

Our research focuses on the hotspot of land change in the Cerrado biome region of the Brazilian state of Bahia with three main objectives. The first is to develop generally applicable methods with accompanying software to quantify and analyze land change and its associated socio-economic drivers and impacts. The second is to examine the expansion of irrigated agriculture as a form of adaptation to climate change. The third is to develop spatially explicit scenario models that inform policy concerning agrarian development, water regulations, and climate change adaptations.

The profession frequently analyzes a time series of a categorical variable such as land cover by using traditional methods that give either too little or too much information for effective interpretation. One traditional approach is to show a trend line that gives the size of a land category as a function of time, which indicates net change but neither gross gain nor gross loss. A second traditional approach is to compute a table that shows how each land category transitions to every other land category during each time interval, which is overwhelming to interpret across multiple time intervals. Therefore, we will build on our existing work to derive novel methods to characterize the gross changes in terms of an interpretable number of components. We will test whether the method will allow researchers to distinguish phases when the processes are stable versus phase changes such as when the government modifies land-use policies.

The social science component of the research will draw upon freely-available political-economic data concerning land ownership, agricultural production, irrigation, and related policies. The data will derive from the Brazilian federal government and Bahia state government agencies. We will undertake fieldwork to validate new remote sensing methods to detect various forms of irrigation, and conduct interviews with government officials, farmers, and community members on the effectiveness of irrigation as climate change adaptation, its social and ecological drivers and impacts, and alternative adaptation strategies.

We will then develop scenarios to model future land change. We will compare baseline scenarios of continuation of recent trends to other scenarios characterized by various irrigation management policies and strong versus weak climate change. The combination of scenarios will generate empirically-based evaluations of multiple policy proposals for climate change adaptation.

The Brazilian Cerrado is one of the most important and threatened ecosystems in the world in terms of carbon fluxes, water resources, biodiversity, and social diversity including indigenous and other traditional communities. Agricultural expansion has become central to the Cerrado’s regional development and global food security. The Cerrado’s northeastern region in western Bahia state of Brazil is one of the most active agricultural frontiers worldwide. Expansion of irrigation is the primary form of climate change adaptation in the region, where rainfall has decreased by 12% since 1980, causing substantial reductions in the Urucuia aquifer and river discharge. Climate change has already pushed 28% of current agricultural lands in the Cerrado out of their optimum climate space. This combination of reduced availability and increased demand for water resources is already triggering socio-environmental conflicts and pushing governance of water resources to the top of policy agendas.