Horticulture notes April 2008
Climate change and implications for horticulture
UK Growers need to adapt and respond to survive the impact of climate change. This was the message from Roger Street, the Technical Director of the UK Climate Impacts Programme (UKCIPS), at a special meeting for horticulture growers hosted by Joan Hamilton, our Edible Crops Adviser.
While weather varies greatly between seasons, the trends of changing climate that are now being observed are global. A warming of the atmosphere is unmistakably evident, from observations of average air and ocean temperatures, the widespread melting of polar snow and ice and a rise in the average sea level worldwide.
Roger presented a number of measured indicators for changing climate, namely that
- mean temperatures in Northern Ireland have risen by around 0.8oC since 1980
- the ‘thermal’ growing season has lengthened by almost 30 days since 1900
- the pattern of rainfall in recent years has changed, with higher winter and lower summer values.
He also stated the main markers that scientists will be closely monitoring in future. “Global temperatures are predicted to increase by 0.2oC on average over the next two decades. Even if greenhouse gas emissions are stabilised at 2000 levels, we can expect a further warming of about 0.1oC per decade. Should emissions continue at present levels, then average temperature rises of 4oC are possible by the end of this century”.
Such significant heating of northern European climates may necessitate the introduction of heat and drought tolerant crop varieties for local production.
But for horticultural growers in N. Ireland there may be opportunities from such change. A number of our competitors are in regions which will become either too hot for production of certain crops or limited by water scarcity. Already some French winemakers are buying land in southern England to establish their next vineyards. Also, crops that were never feasible to grow here before may become economic possibilities.
Stephen Jess, Entomologist with the AgriFood and BioSciences Institute (AFBI), then outlined changes in insect dynamics which could occur as result of climate change. “Although there may be some changes in the significance of particular insects as pests due to global warming, the real impacts are likely to occur due to global trading and cargo traffic.”
Stephen illustrated his point by relating the spread of the western corn rootworm. Prior to 1992 this beetle pest was confined to N America, where its larvae are estimated to cost US agriculture some $1 billion in lost crops and chemical treatments. When the US peace keeping force came to Bosnia in 1992 the corn rootworm was introduced. Within 10 years it had spread through most of Eastern Europe. By 2007 had moved though Italy and France and entered the UK. If this pest spreads to N Ireland the implications for maize crops here would be devastating.
Other foreign species, unknown here at present, could also spread as pests to N. Ireland through a similar mechanism.
Alistair McCracken, AFBI, addressed the issue of plant diseases in the light of global warming. He explained that although plant pathogens were not greatly influenced by temperature changes, climate change could have other effects. The length of particular life stages and rates of development of pathogens could be altered. Moisture stress or heat stress could leave plants less resistant to pathogens and there could be changes in host-pathogen interactions. Unstable weather conditions would make it more difficult to predict disease outbreaks and a rise in the frequency of extreme weather conditions could reduce the effectiveness of pesticides.
Alistair gave examples of diseases which might become more troublesome here, due to higher temperatures. However, he also agreed with the previous speaker that global trade and movement of plants was a more likely route for new pathogens.
