Future Heatwaves A Threat To Aussie Plant Life

A study, published in the journal Global Change Biology, has found that across much of inland Australia plants are near a tipping point in their ability to cope with rising high-temperature extremes. This suggests that future heat-waves could have devastating effects on Australia's flora.

In heatwave conditions, there comes a certain point where plant metabolism begins to be damaged - the temperature where leaf photosynthesis is impaired. This can range from 41.5 °C in Arctic plants to 50.8 °C in the Amazon. Lethal temperatures - the point at which respiration irreversibly declines - are about 10 °C higher.

The world's major productive regions are most likely to be adversely affected by heatwave impacts. - View larger Image (opens in a new window)

Future Heatwaves A Threat To Aussie Plant Life

Weather in September may not feel hot in Australia right now, but over the past year we've experienced the hottest global temperatures on instrumental record. This could spell bad news for Australia's plants.

A study, published in the journal Global Change Biology, has found that across much of inland Australia plants are near a tipping point in their ability to cope with rising high-temperature extremes. This suggests that future heat-waves could have devastating effects on Australia's flora.

"We surveyed plant life around the globe for their high-temperature tolerance," said Professor Owen Atkin of the ARC Centre of Excellence in Plant Energy Biology at the Australian National University, who led the study.

"We show that, while heat tolerance is higher in plants near the equator than in the arctic, the potential for damage is most severe for hot, inland, mid-latitude regions. Here, maximum air temperatures during heat-waves are most extreme".

"Plants growing in the dry, inner regions of Australia are at particularly high risk. We could see dramatic changes to the face of Aussie plant life in the future".

The international team of researchers looked at plants from habitats all over the world, including nineteen remote sites in the arctic, tropics and deserts.

The study is the most comprehensive analysis of heat tolerance in plants to date. By exposing leaves to increasing temperatures during controlled tests, the researchers were able to pinpoint the exact temperatures where leaf metabolism becomes damaged by heat.

They found that two critical processes for plant growth and survival, namely photosynthesis and leaf respiration, were damaged by high-temperature extremes.

We determined the exact temperatures where leaf metabolism is damaged by heat. Though we found that tropical plants are better able to tolerate high temperature extremes than temperate or arctic plants, we were surprised to discover that plants growing in temperate climates of the mid-latitudes were closest to the tipping-point in their ability to tolerate high temperature extremes experienced during heat waves.

"The study suggests high temperatures during heat waves will damage a plant's ability to function, particularly in sun-exposed, upper canopy leaves" said lead author Dr Odhran O'Sullivan.

"This means extreme heat-wave events, predicted to increase in intensity with climate change, could have devastating effects on natural plant populations and ecosystems, and the latitudes at risk will likely expand in the long term".

Co-author Professor Mark Tjoelker of the Hawkesbury Institute for the Environment at Western Sydney University said "the potential for high-temperature heat-damage is greatest during periods of drought, when plants are unable to use water to naturally cool leaves". The findings of the study also have important implications for farmers growing crops in hot, inland regions of Australia.

"We know that crop yields are negatively affected by heat-waves, often when crops are flowering. Our results point towards heat damage to leaves being a further factor contributing to reduced crop yields. The potential for such damage will only increase as global temperatures rise" said Prof. Atkin.

"Because heat-waves are becoming more extreme and frequent, there is an urgent need to improve heat tolerance of leaf metabolism in crops, such as wheat, that are often grown in hot, arid regions".

With funding from the ARC Centre of Excellence in Plant Energy Biology and the Grains Research Development Corporation (GRDC) in Australia, researchers are now using the results of the study to identify wheat varieties capable of better handling heat stress.

The study was performed by an international collaboration of researchers from the ARC Centre of Excellence in Plant Energy Biology at ANU, Western Sydney University, and several leading institutions in the USA, UK, Sweden and New Zealand.

O'Sullivan, O. S., Heskel, M. A., Reich, P. B. (opens in a new window), Tjoelker, M. G. (opens in a new window), Weerasinghe, K.W. L. K., Penillard, A., Zhu, L., Egerton, J. J.G., Bloomfield, K. J., Creek, D., Bahar, N. H. A., Griffin, K. L., Hurry, V., Meir, P., Turnbull, M. H. and Atkin, O. K. (2016), Thermal limits of leaf metabolism across biomes. Glob Change Biol. Accepted Author Manuscript. doi:10.1111/gcb.13477 (opens in a new window).

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