Volunteers
2003 Transcripts
2002
Transcripts
2002 Evaluation
2002
Program
2002
Presenters
2002
Exhibitors
Essays
North Coast horticultural consultant, Peter Hardwick, said he was now including climate change in horticultural planning.
"Climate change is an observable fact of life and it's possible to plan for it. Growers who include climate change strategies into their horticultural enterprise could reap the rewards.
"Many tree crops have a 20 year or greater life expectancy. Within that timeframe we are seeing and expecting big changes in global and regional climate. With fruit and nut trees it's important to anticipate potential impacts from future climate trends."
Possible responses include: selecting crops and varieties with extreme weather tolerance; distributing risk by diversifying crop range; selecting sites which maybe more suitable for cropping in changed climatic conditions; and managing crops for an increase in weather extremes.
Last summer's extreme heat on top of low soil moisture levels caused North Coast crop losses in horticulture, especially to avocado (up to 65% losses), macadamia (25% losses) with serious affects on other susceptible crops including coffee and Davidson's plum.
Severe leaf burning and damage to fruit occurred in many horticultural crops on the North Coast on the very hot days. One long-term avocado grower said it was the worst heat damage he had ever seen.
Dr Marylin Ball, an expert based with the Australian National University said the leaf-burn was consistent with heat-stress induced photoinhibition. This is basically where the plants can not effectively absorb the incoming solar energy due to stress and leaves begin showing burn-like symptoms.
There was a continental 'furnacing' effect, where very hot, low humidity air was directed onto the North Coast ahead of cold fronts coming off the Southern Ocean. Temperatures were as high as 43 degrees Celsius, and humidity very low at 5 to 10 %. This was on top of dry soil conditions.
"The hotter continental air and lower soil moisture levels are consistent with global warming predictions. These events rarely occur under normal conditions, but with climate change we could be facing a much higher frequency of these extremely hot dry events in the usually humid coastal environment."
Many subtropical fruit and nut crops have rainforest origins and are vulnerable to the hot and dry conditions, especially if they are not irrigated.
There is the potential to grow horticultural crops that are less vulnerable to hotter weather extremes, such as some native essential oil crops, and some winter-bearing subtropical fruit crops. However newer horticultural crops are typically disadvantaged by a need for further development and small markets initially.
Mixed species cropping on any single farm is also a way of distributing risks, by offsetting losses in sensitive crops.
Management strategies for hotter weather can also include water conservation, irrigation, mulching, overhead nurse-tree cropping, and canopy reduction in tree-cropping. Overhead shade-cloth reduces heat stress with summer market gardening.
In eastern Australia we have to contend with the natural extremes of El Nino
and La Nina. The experience will be useful in preparing for climate change
extremes, but we also need to cautiously try some new ideas, such as re-evaluating
high water table environments for cropping.
Extra vigilance is required with the possibility of extreme heat once again impacting on subtropical suffering dry soil conditions. Extreme heat-waves are more likely to occur in El Nino events, such as January 1994.
17/10/2002
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