Climate change, agriculture and decreasing yields

By Peter Griffin 31/03/2014

The Intergovernmental Panel on Climate Change’s Working Group II report is out and paints a stark picture for agricultural productivity in a warming world.

Screen Shot 2014-03-31 at 5.11.31 PMOver at the Science Media Centre, we gathered reaction from climate scientists here and in Australia and the UK. Much of the commentary focuses on things like climbing emissions, sea level rise and extreme weather events.

But the press conference in Yokohama today that accompanied the release of the report, paid a lot of attention to the impact climate change will have on efforts to feed a burgeoning global population, as it impacts on crops and fisheries that sustain billions of people.

You see, scientists predict that yields for some major crops, particularly food grains that form the basis of a staple diet for millions, will begin to decline later this century.

Here’s how the IPCC puts it in its summary for policymakers:

Source: IPCC Assemmment Report 5 - WG2 Summary for Policymakers
Source: IPCC Assessment Report 5 – WG2 Summary for Policymakers

The Guardian, in the first of a two-part series on the issue of crop yields, points to research recently released that backs up the high-level statements of the IPCC, that we face falling crop yields in a warming world.

The researchers found this by comparing results from almost 100 independent studies—more than double the number used in the IPCC’s fourth assessment—that measured the impact of higher temperatures on three of the globe’s primary staple crops: maize, wheat, and rice. It’s currently the largest dataset we have that demonstrates how crops will respond to changing climates, and it suggests that decreases in yields will grow larger, affect both temperate regions and the tropics, and become increasingly erratic as the weather turns more unpredictable too.

Once mid-century hits, crop losses of up to 25% will become more commonplace, as well—a number that does account for basic mitigation efforts in farming regimes.

The green revolution saw, over the past 50 years, dramatic increased in agricultural productivity, which has fueled the world’s population growth. The suggestion from the latest IPCC report is that we will struggle to maintain this productivity growth as the climate changes, leading to rising tensions over food security. Humans have engineered their way out of lean food supply before. Can we do it again?

Key points of the IPCC WR-II report

* In many regions, changing precipitation or melting snow and ice are altering hydrological systems, affecting water resources in terms of quantity and quality

* Glaciers continue to shrink almost worldwide due to climate change, affecting run-off and water resources downstream

* Climate change is causing permafrost warming and thawing in high-latitude regions and in high-elevation regions

* Many terrestrial, freshwater, and marine species have shifted their geographic ranges, seasonal activities, migration patterns, abundances, and species interactions in response to ongoing climate change

* Based on many studies covering a wide range of regions and crops, negative impacts of climate change on crop yields have been more common than positive impacts

* Climate change has negatively affected wheat and maize yields for many regions and in the global aggregate. Effects on rice and soybean yield have been smaller in major production regions and globally

* Climate-related hazards affect poor people’s lives directly through impacts on livelihoods, reductions in crop yields, or destruction of homes and indirectly through, for example, increased food prices and food insecurity

* Freshwater-related risks of climate change increase significantly with increasing greenhouse gas concentrations. The fraction of global population experiencing water scarcity and the fraction affected by major river floods increase with the level of warming in the 21st century

* Climate change over the 21st century is projected to reduce renewable surface water and groundwater resources significantly in most dry subtropical regions, intensifying competition for water among sectors

* Due to sea-level rise projected throughout the 21st century and beyond, coastal systems and low-lying areas will increasingly experience adverse impacts such as submergence, coastal flooding, and coastal erosion

* Some low-lying developing countries and small island states are expected to face very high impacts that, in some cases, could have associated damage and adaptation costs of several percentage points of GDP

* Due to projected climate change by the mid 21st century and beyond, global marine-species redistribution and marine-biodiversity reduction in sensitive regions will challenge the sustained provision of fisheries productivity and other ecosystem services

* Spatial shifts of marine species due to projected warming will cause high-latitude invasions and high local-extinction rates in the tropics and semi-enclosed seas

* Species richness and fisheries catch potential are projected to increase, on average, at mid and high latitudes and decrease at tropical latitudes

* Climate change will impact human health mainly by exacerbating health problems that already exist

* Throughout the 21st century, climate change is expected to lead to increases in ill-health in many regions and especially in developing countries with low income, as compared to a baseline without climate change

* For the major crops (wheat, rice, and maize) in tropical and temperate regions, climate change without adaptation is projected to negatively impact production for local temperature increases of 2°C or more above late-20th-century level


0 Responses to “Climate change, agriculture and decreasing yields”