Climate Change And Impact On World Agriculture
The Earth’s climate has become increasingly warmer, primarily from increasing greenhouse gas emissions. Climate change—a phenomenon synonymous with global warming and the greenhouse effect—is projected to continue. The major effects of climate change will be
- a rise of 1.5°–5.8°C in the mean temperature by the end of the twenty-first century;
- an increase in the frequency of droughts;
- an increase in sea levels and frequency of floods and heavy rains; and
- an alteration of wind directions (IPCC, 2001; 2014).
Predictions forecast higher growing season temperatures in the tropics and subtropics that will exceed the most extreme seasonal temperatures recorded in the 1900s. Thus, with these anticipated ipmacts, climate change is expected to exacerbate the already serious challenges to food security and economic development around the world.
Climate Change Impacts On Arthropod Pests And Biological Control
On average, 30–50% of yield losses in agriculture are caused by pests despite the application of pesticides (Oerke, 2006). Climate change will aggravate these already serious challenges to food security by virtue of increasing pest problems and related losses in crop yield and quality.
As exothermic organisms, insect pests cannot internally regulate their own temperature and depend on the temperature to which they are exposed. Under climate change, then, temperature is the dominant abiotic factor directly affecting herbivorous insects. Any temperature increase—depending on a species’ optimal temperature of development—is expected to magnify pest pressure in agricultural systems through:
- Range expansion of native pests and invasion by new pests;
- Accelerated pest development leading to more pest generations per season and per year;
- Disruption of the temporal and geographical synchronization of pests and beneficial insects, which will increase the risk of pest outbreaks;
- Promotion of minor pests to primary pests through reduced host tolerance and changes in landscape characteristics and land-use practices; and
- Increases in the susceptibility of drought-stressed plants to pests.
Depending on complexity and species richness, agro-ecosystems can have strong potential to provide a high level of natural biological control. Hence, ecosystem complexity can increase ecosystem resilience to pest outbreaks. Several studies indicate, however, that climate change can dissociate natural enemy-pest relationships due to a higher sensitivity of higher trophic levels to climatic variability or from different temperature optima compared with pests. In this respect, divergences in the thermal preferences of pests and associated natural enemies can lead to a disruption of the temporal or geographical synchronization, increasing the risks of host outbreaks. These changes might also reduce the efficacy of successful classical biocontrol programs.