Plants Response to Climate Change
Plants response to climate change is dictated by a complex set of interactions to CO2, temperature, solar radiation, and precipitation. Each crop species has a given set of temperature thresholds that define the upper and lower boundaries for growth and reproduction, along with optimum temperatures for each developmental phase. Plants are currently grown in areas in which they are exposed to temperatures that match their threshold values.
Plants Response to Increased Temperatures
As temperatures increase over the next century, shifts may occur in crop production areas because temperatures will no longer occur within the range, or during the critical time period for optimal growth and yield of grain or fruit.
For example, one critical period of exposure to temperatures is the pollination stage, when pollen is released to fertilize the plant and trigger the development of reproductive organs, for fruit, grain, or fiber. Such thresholds are typically cooler for each crop than the thresholds and optimal for growth.
Pollination is one of the most sensitive stages to temperatures, and exposure to high temperatures during this period can greatly reduce crop yields and increase the risk of total crop failure.
Plants exposed to warm nighttime temperatures during grain, fiber, or fruit production also experience lower productivity and reduced quality.
Increasing temperatures cause plants to mature and complete their stages of development faster, which may alter the feasibility and profitability of regional crop rotations and field management options, including double-cropping and use of cover crops.
Faster growth may create smaller plants, because soil may not be able to supply water or nutrients at required rates, thereby reducing grain, forage, fruit, or fiber production.
Increasing temperatures also increase the rate of water use by plants, causing more water stress in areas with variable precipitation.
Estimated reductions in solar radiation in agricultural areas over the last 60 years are projected to continue due to increased cloud cover and radiative scattering caused by atmospheric aerosols. Such reductions may partially offset the temperature-induced acceleration of plant growth.
For vegetables, exposure to temperatures in the range of 1°C to 4°C above optimal for biomass growth moderately reduces yield, and exposure to temperatures more than 5°C to 7°C above optimal often leads to severe, if not total, production losses.
Climate affects microbial populations and distribution, the distribution of vector-borne diseases, host resistance to infections, food and water shortages, and food-borne diseases
Plants Response to Decreased Temperatures
An increase in winter temperatures also affects perennial cropping systems through interactions with plant chilling requirements.
All perennial specialty crops have a winter chilling requirement (typically expressed as hours below 10°C and above 0°C) ranging from 200 to 2,000 cumulative hours. Yields will decline if the chilling requirement is not completely satisfied because flower emergence and viability will be low.
Projected air temperature increases for California, for example, may prevent the chilling requirements for fruit and nut trees by the middle to the end of the 21st century.
In the Northeast United States, perennial crops with a lower 400-hour chilling requirement will continue to be met for most of the Northeast during this century, but crops with prolonged cold requirements (1,000 or more hours) could demonstrate reduced yields, particularly in southern sections of the Northeast.
Climate change affects winter temperature variability, as well; mid-winter warming can lead to early bud-burst or bloom of some perennial plants, resulting in frost damage when cold winter temperatures return.
Plants Response to Increase Carbon Dioxide (CO2) Levels
Increasing carbon dioxide (CO2) in the atmosphere is positive for plant growth, and controlled experiments have documented that elevated CO2 concentrations can increase plant growth while decreasing soil water-use rates.
The effects of elevated CO2 on grain and fruit yield and quality, however, are mixed; reduced nitrogen and protein content observed in some nitrogen-fixing plants causes a reduction in grain and forage quality. This effect reduces the ability of pasture and rangeland to support grazing livestock.
The magnitude of the growth stimulation effect of elevated CO2 concentrations under field conditions, in conjunction with changing water and nutrient constraints, is uncertain. Because elevated CO2 concentrations disproportionately stimulate the growth of weed species, they are likely to contribute to increased risk of crop loss from weed pressure.
The effects of elevated CO2 on water-use efficiency may be an advantage for areas with limited precipitation.
Other changing climate conditions may either offset or complement such effects. Warming temperatures, for instance, will act to increase crop water demand, increasing the rate of water use by crops.
Crops grown on soils with a limiting soil water-holding capacity are likely to experience an increased risk of drought and potential crop failure as a result of temperature-induced increases in crop water demand, even with improved water-use efficiencies.
Conversely, declining trends of near-surface winds over the last several decades and projections for future declines of winds may decrease evapotranspiration of cropping regions.
How to Combat Climate Change Problem in response to Plant Growth?
Crops and forage plants will continue to be subjected to increasing temperatures, increasing CO2, and more variable water availability caused by changing precipitation patterns. These factors interact in their effect on plant growth and yield.
A balanced understanding of the consequences of management actions and genetic responses to these factors will form the basis for more resilient production systems to climate change.
Due to the complexities of these relationships, integrated research and development of management practices, plant genetics, hydrometeorology, socio-economics, and agronomy is necessary to enable successful agricultural adaptation to climate change.
While many agricultural enterprises have the option to respond to climate changes by shifting crop selection, development of new cultivars in perennial specialty crops commonly requires 15 to 30 or more years, greatly limiting that sector’s opportunity to adapt by shifting cultivars unless cultivars can be introduced from other areas.