For many situations, success depends on monitoring and managing a crucial balance between the beneficial and the pest organisms. This balance is primarily temperature dependent: warmer temperatures mean faster insect development. However, the rates of change will be different for different organisms, so affecting the population balance between them.
But according to speakers at Simon Fraser University in mid-February1, climate change will affect pest and disease spread, and therefore our biological-based management strategies. The devastatingly rapid spread of Mountain pine beetle through forestry plantations in B.C. is just one example, but closer to home for greenhouse growers, over-wintering of aphids, lygus and whiteflies may become much more of an issue.
On the larger scale, we are increasingly seeing “immediate” results of climate change:
- More severe storms (if the air is warmer by 1-2 C, it holds much more water, and so we get more dramatic rainfall events).
- Most of the warmth actually increases in the winter temperatures. Hence, survival of pests outdoors is much greater. Consequently, insect pests are moving into new geographical areas.
- Perhaps our biggest challenge will be, or already is, food security. Yields of wheat and rice in tropical regions is predicted to worsen, yet ironically it could be better in temperate regions and we may see production switching to such crops in the near future.
- As we’ve already said, over-wintering of existing pests. Of course, we might see over-wintering of beneficial species, too.
- New pest species affecting our crops.
- New crop species too, both edibles and ornamentals.
- More stressed (and therefore more vulnerable) crops.
- Consequently a need for continued research for more beneficials working on different pests in different crops.
- Changes to production economics (heating/cooling costs in greenhouse systems maybe). This may make business planning and crop forecasting more difficult.
- Changes to the traditional crop seasons. Many outdoor crops in B.C. this winter are growing at least a month ahead of normal schedule. Of course, it is the opposite in many eastern parts of North America.
Incidentally, we’re not just talking about plant pest and diseases issues here. We often don’t think about it, but most human diseases are seasonal. Adults typically get flu once every five years. Perhaps that will change. Vectored diseases and their consequences are common in the warmest climates: dengue fever, malaria and the often consequent diarrhea and malnutrition are all affected by climate change. The geographical range of these diseases will change.
Furthermore, algal blooms and aerial pollution are linked to climate change, as are direct effects on humans from global temperature changes: 70,000 deaths in Europe were attributed to a heat wave as were 11,000 deaths due to famine in Egypt because a heat wave meant there were poor yields of wheat from Russia.
Don’t think climate change is happening? Then tell me that the commercial crops of paddy rice and tea that we have in B.C. are “normal.”
1Dr. Kristie Ebi, University of Washington.
Gary Jones is co-chair of horticulture at Kwantlen Polytechnic University, Langley, B.C. He serves on several industry committees and welcomes comments.