What ecosystem is the most under threat?
Climate change is a major threat to Australia’s coastal marine ecosystems, such as kelp forests, seagrasses and coral reefs. Each of these habitats needs shallow sunlit waters to photosynthesise, and so they cannot move into deeper cooler waters to escape warming temperatures or migrate south like mobile animal species.
Some ecosystems are more ‘exposed’ to change than others. Warming does not occur at the same rate everywhere. Some regions like the Arctic and south-east Australia are warming very fast and therefore have ‘high exposure’ to climate change, whereas other regions are warming very slowly.
The other way we can tell how threatened a plant or animal is is to find out how close it is living to its ‘thermal tolerance limit’ - or the warmest temperature at which it can survive. A population living in a place that is already as hot as it can handle will not respond well to further warming. But if it is living in a place that is cooler than it can tolerate, it is more likely to survive. In Australian kelp forests for example, many of the same species can be found from Tasmania up to northern NSW. Tassie reefs sit at the cool end of this distribution. As a result, many species on Tasmanian reefs are likely to respond quite well to climate change for some time. In NSW by contrast, these same species are at the warm edge of their distribution, and so they may not survive any further warming in NSW.
Kelps, corals, seagrasses and mangroves are all examples of what we call ‘foundation species’. The loss of corals from a coral reef or kelps from a kelp forest fundamentally changes the ecosystem and species that it can support.
Globally, coral reefs are considered to be very threatened from climate change as they are already living close to the warm limits that corals can survive at. As a result, summer temperatures that 1-2ºC above a typical summer can lead to coral bleaching and death. Elsewhere in the world, kelp forest ecosystems are considered to be more tolerant to warming. In Australia, however, coral reefs, kelp forests and seagrass ecosystems have all been severely impacted by warming in different places.
