The world has warmed over the last 50 years and is likely to continue to do so over the coming century. This poses problems for life on land and in the ocean, since most species have a defined range of temperatures within which they can live.
When temperatures exceed the upper limit for a particular species in a particular location, that species can no longer live there. Likewise, places can become newly habitable when temperatures become warmer than a species’ lower limit.
As climate change unfolds over the next century, plants and animals will need to adapt or shift locations to track their ideal climate.
In research published today in Nature, CSIRO and an international team of scientists revealed global maps showing how fast and in which direction local temperatures have shifted over the past 50 years. For water temperatures, two future scenarios were investigated as well (based on the 2007 IPCC climate models ‘business as usual’ and ‘1.75°C temperature increase’).
This research points to a simpler way of looking at climatic changes and their likely effects on biodiversity.
On the move
Our changing climate is creating new thermal environments in some areas and in others existing environments may disappear.
Over the past few decades numerous fish and invertebrate species living in the southern hemisphere have already shifted their geographic distribution towards cooler regions. On land, species have started to seek relief from warmer conditions by moving closer to the coast, to higher elevations, to shaded hill aspects or further from the equator.
Potential barriers to migration
Geographic features such as coastlines and mountain ranges can act as barriers or magnets, influencing migration patterns.
For example, the dry, flat continental interior is a hot, arid region where species already exist close to the margin of their thermal tolerances. Some species driven south from monsoonal northern Australia in the hope of cooler habitats may perish in the much drier habitats of desert Australia
The central lowlands of eastern Australia that drain the Lake Eyre Basin, are a source of new thermal climates and species migration may sweep in all directions – toward the coast, south, inland and progressively up mountain ranges. This is a complex region including parts of the Murray Darling Basin around which rapid thermal shifts are occurring and we can expect considerable climate migration.
Species migration can have important consequences for local biodiversity. For example, warming waters and a strengthening of the East Australian Current have mobilised the Long-spined Sea Urchin (Centrostephanus rodgersii), previously only found as far south as southern NSW, to invade the eastern Tasmania coast. This has resulted in the decline of giant kelp forests with knock-on effects for commercially-fished rock lobsters.
What’s more, along the east coast of Australia the direction of the climate pathways coincides with the direction of flow of the East Australian Current, therefore increasing the potential for dispersal of climate migrants. It is not surprising that some of the first evidence of climate change affecting marine species’ distributions in Australia has come from south-east waters, with range shifts observed in around 30% of coastal fish species.
What can be done?
Knowing where vulnerable areas occur can help focus conservation efforts and information management decisions.
Areas of slow temperature shifts may be better suited to protecting endemic species or long-lived structural species (such as those forming forests or coral reefs). Areas exposed to significant pressures from climate change may need help to enable climate-driven migration. For species unable to move, assisted movement to new more acceptable places may be needed. For example, active translocation of species, given due care to potential negative ecological and production consequences.
It is important to note that this study cannot be used as a sole guide as to what to do in the face of climate change. Biological factors such as a species’ capacity to adapt and disperse need to be considered. But in an unprecedented period of climate change, economic development and fast-growing demand on an already pressured planet, we need to act fast to ensure most of the world’s living resources survive that change.
The study was undertaken by CSIRO’s Dr Elvira Poloczanska, Associate Professor Anthony Richardson and Dr Kristen Williams with a team of 18 international researchers from Australia, Canada, Germany, Spain, UK and USA.