(CN) — Farmers are facing a tough decision in the face of climate change: Deal with low yields from the crops they depend on, or plant drought-resistant strains that leave them prone to income instability.
Increasing water stress and rising temperatures decrease yields, as suboptimal conditions force plants to expend their energy on survival rather than growth. A study published Friday in the journal Nature examines these conditions in the Yakima River Basin in Washington state. The authors investigated the impacts of climate change on regional agriculture and whether drought-resistant crop varieties could increase farmers’ otherwise diminishing returns.
Rising global temperatures are reducing the available water supply in regions that depend predominately on snowfall for crop irrigation. This places farmers in a precarious position, deciding either to adapt to the decreased yields they will face in an age of global warming, or to plant newer drought-resistant crop varieties that inevitably lead to a more volatile income stream. Because these crops typically produce greater yields when water is restricted, an especially bad season could leave farmers with staggering, unanticipated and uninsured losses.
“Typical and best-case annual yields are much higher,” said Jennifer Adam, Berry Distinguished Professor of civil and environmental engineering at Washington State University and co-author of the study, in a statement accompanying the study. “But climate change still is likely to cause severe droughts where current water management institutions in the Yakima River Basin simply cannot provide enough water, and there are severe worst-case crop failures.”
Researchers found a constant trade-off between yield and income stability. They recommend simultaneously improving crop varieties and water delivery through an improved system of water rights and infrastructure development. Relying solely on drought-resistant strains of crops would leave farmers subject to the whims of an unpredictable water supply and place them in an especially vulnerable position during a dry year.
“Our findings show that farmers who adapt to climate change by planting improved crop varieties may potentially increase their expected mean annual productivity in an altered climate, but remain strongly vulnerable to irrigation water shortages,” note the authors.
Nearly 50% of agriculture production depends on irrigation, despite accounting for only 20% of cultivated lands. Irrigated agriculture has expanded by leaps and bounds in the past 50 years and significantly contributes to the global food supply necessary to feed Earth’s ever-increasing population.
Surface water accounts for 62% of the total water supply used in irrigated agriculture, and that predominately depends on cycles of snowfall and melt. Snow falls in the mountains, runs through rivers, streams and creeks, which then gets diverted and utilized by nearby farmers. Few crops may grow in the Rockies, Cascades or the Sierra Nevada, but the snowpack that accumulates in these ranges is vitally important for national food production. A warming climate swaps that snowfall for rain, which further melts the snowpack and leads to a one-time water bonanza instead of the steady seasonal trickle that farmers rely on.
Despite increasing levels of CO2 that typically raise yields, the knock-on effect of elevated temperatures leads to an overall decline in food production throughout regions that depend on seasonal snowmelt for a steady water supply. This accelerated growth rate is also detrimental to certain staples, such as corn, wheat and potatoes, as it leaves them less time to photosynthesize and thus stunts their foliage production. These conditions are shortening the effective growing season for many farmers — forcing them to do more with less — though new strains currently being developed aim to extend the growing period of these crops and allow them to reap the benefits of rising CO2 levels.
But they need regular, reliable water.
Quantifying shifts in water availability requires that modeling frameworks account for water storage facilities, institutional water rights and environmental regulations. Each of these potentially limits the usefulness of previous simulation-based assessments and do not address the specific conditions unique to various agricultural regions.
Patrick Reed, professor at Cornell's School of Civil and Environmental Engineering, specializes in modeling climate change. His team built on previous work by Washington State University focused on modeling the connection between crop growth and development, land-surface hydrology and river-system processes. Reed’s model simulates dam operations and prioritizes water allocation throughout the Yakima River Basin.
"The models show that year-to-year variability in expected crop yields goes down because the difference between the best and worst case yields is reduced," said Keyvan Malek, a postdoctoral researcher in Reed's group and lead author of the study, in a statement accompanying the study. "While this is not a positive result, year-to-year fluctuations in crop yield revenue are strongly important in how crop insurance programs balance revenue fluctuations."
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