Worry over effect of climate change on kiwifruit crops

A major study is underway to assess the impact of global warming on the Bay of Plenty after predictions of a significant decline in the viability of kiwifruit -- a key economic driver in the region.

Environment BOP is spending $50,000 to draw up local scenarios based on the rapidly expanding volume of evidence being accumulated by climate scientists in New Zealand and overseas.

There is now consensus among world scientists that changes in temperature and rainfall are inevitable, with new and stronger evidence that most of the warming was attributable to human activities.

Environment BOP resource planner Amanda Hunt said a case study on kiwifruit by the Ministry for the Environment showed the crop needed winter chilling to promote bud break and produce good numbers of fruits per vine.

Using the upper-end of New Zealand climate change predications, rising temperatures would lead to a significant decline in the viability of kiwifruit in the Bay of Plenty from 2050 onwards.

Under a more optimistic scenario, there would be little change in the crop's viability for the rest of the century.

The study said the effectiveness of chemicals which artificially break vine dormancy was expected to decline from 2040 as winters grew milder.

Using upper-end of projections, Hawke's Bay, Nelson and Marlborough would start to overtake the Bay of Plenty as the premier kiwifruit growing regions from 2040 onwards.

Growing conditions in the other major kiwifruit producing countries may also become marginal, so it was vital that New Zealand planned well to make the most of economic opportunities and risks posed by climate change.

One solution was to breed cultivars that adapted better to warmer winters: "This is not currently a high priority for the kiwifruit industry, but it will need to become so over the next 10 to 20 years," the case study said.

Ms Hunt said the main climate change predictions for New Zealand were increased westerly flows, sea levels rising 30cm to 50cm, more frequent heavy rain, temperatures rising between 1degC and 2degC, fewer frosts and rising snowlines.

Ms Hunt said th e challenge would be to reach a level of accuracy predicting whether it would rain more in one area than another. This meant looking at local factors such as the topography.

"The earlier we start thinking about it, the better prepared we will be," she said.

The study will be a valuable pointer for local authorities planning major long-term infrastructural projects, such as what diameter pipes they should be used on stormwater systems, or roading along coastal areas.

The study would also look at the implications on ecosystems, such as changes in the range of some species. Plants had an optimal temperature and rainfall range and if it got too hot, they died out or retreated up hillsides.

Another impact of climate change would be on human, animal and plant health. Warmer weather would bring new opportunities for accidentally introduced pest species like disease-carrying mosquitoes which at the moment could not survive because it was too cold in winter.

There had already been episodes with the mosquito which carried dengue fever.

- BAY OF PLENTY TIMES