Three agricultural societies recently published a position statement on climate change. The American Society of Agronomy (1), the Crop Science Society of America (2) and the Soil Science Society of America (3) released a statement in May of 2011. The information below is taken from the statement which can be found in its entirety this link.
The position statement begins, “A comprehensive body of scientific evidence indicates beyond reasonable doubt that global climate change is now occurring and that its manifestations threaten the stability of societies as well as natural and managed ecosystems. Increases in ambient temperatures and changes in related processes are directly linked to rising anthropogenic (4) greenhouse gas (GHG) concentrations in the atmosphere.”
It goes on to state that “The potential related impacts of climate change on the ability of agricultural systems, which include soil and water resources, to provide food, feed,fiber, and fuel, and maintenance of ecosystem services … as well as the integrity of the environment, are major concerns.”
Moreover,the report states that crop production will face increasing challenges linked to climate change. Even though long-term projections suggest that temperatures will increase gradually, potential increases in variations of temperature and rainfall can produce profound impacts on food and energy security. In near-term decades, higher CO2 may provide some benefits to plant growth and water use, but these are likely to be offset by negative effects of rising temperatures and altered rainfall,especially in subsequent decades. Understanding the impact of climate change variables and their progressive interactions is critical to developing agricultural systems that will enhance productivity even in a changing climate.
Global temperatures rose 1.25 degrees Fahrenheit (0.75 degrees Centigrade) in the 20th century, and are projected to increase 3.22 to 7.20 degrees Fahrenheit (1.8 to 4.0degrees Centigrade) by the end of the 21st century. Changes in temperature have already begun to affect crops, water availability, and pests in some areas. Such changes have advanced the spring green-up of perennial crops in the Northern Hemisphere and contributed to an increase in forest fires and pests in North America.
Climate Effects on Crops
The report outlines four major ways in which climate changes impact crops.
- Higher temperatures and heatwaves affect the growth and development of crops, influencing potential yields. An example is the number of days a crop is exposed to temperatures exceeding specific thresholds during critical growth stages such as flowering, pollination and grain filling.
- Changes in the patterns of precipitation alters water supply for crops. Climate change is expected to destabilize pre-existing rainfall regimes in many regions, resulting in changes in duration and intensity of flooding episodes and period of drought.
- Increased atmospheric carbon dioxide (CO2)concentrations may have positive effects on some crops, the effects being species-dependent. The photosynthesis, growth, and yield of C3plants such as wheat and rice tend to benefit more from high CO2 than doC4 plants such as corn. Higher CO2 in the air also increases the efficiency of water use by crops.
- Changes in temperature, precipitation and CO2 will interact with other environmental stresses such as ozone, which tend to reduce crop productivity.