What climate change will do to our forests

24 October 2017
Dr Cate MacInnes in our forest

Cate Macinnis-Ng researches the impacts of drought on New Zealand's landscape, and rising temperatures on the city of Auckland

It is appropriate that Auckland is taking part in the global Climathon at the end of this month because - and let there be no doubt about this - climate change will take its toll on our highly coastal city.

Rising sea levels are likely to have the greatest impact in the shortest time period, especially when high tides coincide with severe storms. But droughts are also on the rise, in Auckland and other dry parts of Aotearoa New Zealand, and they are increasing in frequency and severity according to regional climate change projections.

Potential impacts of drought include water scarcity in our water supply catchments, reductions in productivity of food crops and health declines for native vegetation. The 2013 drought cost an estimated $1.3 billion in lost agricultural production but the impact on natural landscapes, including forests, wetlands and other rarer ecosystems, is less clear. Probable effects could be reductions in carbon uptake, slowing of nutrient cycles and, in the worst cases, death of vulnerable plants.

To get a clearer picture of the effects these droughts will have on our natural landscape, my research team is exploring native plant responses to dry periods using several approaches. First, we have established baseline responses of plant water use and growth patterns to current daily and seasonal variations in climatic conditions. We use manipulative experiments (in the shade house and the field) to dry plants while we measure their responses to define stress limits. Finally, we are using remote sensing to look at the distribution of different impacts across different types of forest.

So far, we are finding some good evidence that native forests are reasonably resilient when it comes to drought – but we don’t know if they can survive more severe or frequent droughts.

What we do know is that forests can be a fantastic solution to a changing climate because they capture and store CO2 from the atmosphere. But if forests are destroyed by fire or die during drought, the carbon is lost back to the atmosphere. Our best solution is to reduce greenhouse gas emissions. We need to get smart about energy and agricultural emissions. We also need to find ways to protect our coastal areas or at least stop building houses on coastal sand dunes.

I commend Auckland Climathoners for their determination and drive to help ensure our city has a bright future. And I hope our native trees and vegetation stay top of their minds as the creativity, collaboration and solution-focused thinking, doing and making begins.

The Auckland Climathon will be hosted by the University of Auckland at Unleash Space on the city campus from Friday night October 27 to Saturday night October 28. It will run in conjunction with events in Wellington, Christchurch and 230 other cities around the world. It is free and open to open to everyone, aged 18 plus, who has an interest in creating a new energy future for the city.

Dr Cate Macinnis-Ng
is senior lecturer of Biological Sciences in the University of Auckland's Faculty of Science. Her current research projects are on drought impacts on native vegetation, and carbon fluxes in native forests.

Used with permission from NewsroomWhat climate change will do to our forests published on Tuesday 24 October 2017.