As climate changes, animals move fast to escape the heat

October 10, 2013 by Stephen Williams & Brett Scheffers, The Conversation
This rare white lemuroid possum is just one of the species that will see dramatic effects of climate change. Credit: Mike Trennery

Australia is already feeling the effects of climate change, with record-breaking temperatures not just over summer, but over the past 12 months as well. Research suggests that such events are many times more likely thanks to climate change.

The IPCC fifth assessment report on science found evidence for climate change is unequivocal. The impacts of increasing frequency and intensity of on people and our environment are real and undeniable. But what's happening to our animals and plants? Our research in Queensland is starting to give us some clues.

Warning from the rainforest

More than 10 years ago, we made predictions that the animals in the World Heritage-listed rainforests of north Queensland faced a grim future.

In the Queensland Wet Tropics we've compiled one of the most robust databases on species distributions on Earth, enabling us to vastly improve our understanding of these systems and to monitor changes.

Animals are adapted to specific ranges. As temperatures increase thanks to climate change, we predicted animals and plants would move up mountains as they attempted to remain at cooler temperatures. Eventually they would reach the top of the mountain and have nowhere else to go.

Unfortunately, our predictions are now starting to come true.

In our monitoring in the world heritage rainforests, we recently confirmed that at least 13 bird species and four species of ringtail possums have moved up the mountains in order to remain at cooler temperatures just as we predicted a decade earlier. Strikingly, their shifts are detectable over just 10 years with only a fraction of the temperature change that we will experience over coming decades.

Thus, small changes in climate can have more severe effects on biodiversity than previously though.

In addition to a steady increase in mean temperature, climate also affects animals via the increasing severity and frequency of extreme events such as heat waves.

For example, our research over the past 10 years showed that lemuroid ringtail possums have declined in the northern mountain ranges. The culprit is heatwaves, which have increased in intensity and length over the past 50 years. In the summer of 2005, maximum temperatures went over the possum's physiological tolerance for 27 days in a row. The possums couldn't escape, and widespread deaths ensued.

Unlike heat extremes, increasing average temperatures will slowly but inexorably push species up mountain sides where they will eventually run out of room and shelter. We now have evidence that numerous species in the Wet Tropics region will share similar fates to the Lemuroid Possum.

Beyond Australia

Our recent work in the Philippines has added another dimension to our knowledge of climate change and its effects on rainforests.

We found that rainforest vegetation creates a climate gradient – much like the gradient you can find going up a mountain. This gradient is far steeper than changes in climate that may occur over hundreds of metres of elevation, or hundreds of kilometres of latitude. The tiered vegetation within just 20 metres of rainforests can reduce temperatures by more than 2C and increase humidity by over 10%.

Animals and plants organise themselves along this gradient, living in the part they find most comfortable.

But when the rainforest heats up thanks to climate change, animals and plants move down the trees because, at low elevations at least, the canopy becomes too hot. We call this process "flattening", and it will have severe consequences for biodiversity. For example, we show that as animals move towards the ground in response to warmer temperatures, the density of animals on the ground may increase by over 80%. This is like trying to fit 100 people in a bus that only has space for 20 – it just doesn't work.

Climate change may create an extinction zone in the lowlands that starts in the canopy and moves down towards the ground. As the Earth continues to warm, this zone will then expand upwards in elevation. This novel finding is relevant to many ecosystems in Australia and globally.

What to do now

So how do we deal with these dire forecasts? Both mitigation and adaptation will be critical for saving species.

Here in Australia and abroad we've discovered that intact forests that offer a variety of complex structures can reduce the severity of extreme climate events. These structures are like small air-conditioning units in the rainforest that smaller species can use. Thus, intact and protected will be critical for species adaptation and safeguarding biodiversity as the Earth warms.

But even this isn't enough in the long term. By 2100 no amount of air-conditioning will offset the temperatures predicted.

Species loss offers a compelling argument to act now on mitigation policies like cap and trade, offsets and emissions reductions.

Why should we do so? The Wet Tropics of Queensland are a globally-significant world heritage area that provide habitat for species found nowhere else on earth, including nearly 100 unique mammals, birds, reptiles and frogs, and thousands of species of insects and plants.

The region is also incredibly valuable economically. Eco-tourism stimulates the regional economy to a tune of A$4-5b a year. And our fresh clean drinking water comes primarily from these forests.

We could say the same about other ecosystems in Australia and the and plants that are part of them. Without mitigation and adaptation, many will suffer from , and that's bad news for us too.

Explore further: Stable temperatures boost biodiversity in tropical mountains

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