The Challenge To Understand Contemporary Impacts

While significant coastal degradation has occurred over the twentieth century it is difficult to unambiguously attribute the relative role of climate change. Most degradation has occurred on coasts that are influenced by one or more non-climate related drivers such as ongoing tectonic or isostatic adjustments, or, increasingly often, as a result of human activities. Further, the magnitude of climate change to date remains relatively small. In the next few decades, global warming will continue and is expected to accelerate, resulting in climate-induced impacts becoming more apparent.

In some coastal regions it is possible to discriminate between those effects that can already be attributed to climate change. Rising air and sea surface temperatures have resulted in detectable impacts on polar and tropical coasts. There is an emerging consensus that the increased frequency of bleaching on coral reefs is related to higher sea surface temperatures. Melting of sea ice and permafrost in high latitudes results from increased temperatures, and this is related to rapid erosion of polar coasts. However, these coasts were already experiencing extensive erosion, and there is no clear procedure for differentiating how much erosion would have been occurring because of ongoing factors, such as isostatic adjustments of the land, and how much additional retreat has occurred because of climate change.

A significant component of global-mean sea-level rise also results from global warming, primarily because of thermal expansion, but with a component from ice melt. Discriminating the impacts of the global-mean sea-level component at regional and local scales where other contributions to relative sea-level change are of variable importance remains problematic. This presents a challenge to further test and refine our understanding about the impacts of climate on coasts, so that better predictions can be made and management plans put in place to respond to the anticipated impacts.

To meet this challenge, it will be necessary to continue and expand monitoring of coastlines, including both the climate and non-climate drivers, and the responses of coastal systems. Climate change is a global phenomenon, and therefore this monitoring and analysis needs to consider changes over broad scales. There will be an increasing role for more sophisticated remote sensing which will be an important tool [34,60]. Comparative studies offer the opportunity to assess sensitivity, comparing those coasts with intense human pressures with more pristine counterparts in less densely populated regions. However, as indicated above, the indirect effects of human modification of the Earth are leaving a pervasive signal in even these remote places; global sea-level change effects those coasts that are uninhabited as well as those that are intensively developed. Studies of analogues of climate change and sea-level rise are also relevant, such as relative sea-level rise on subsiding coasts which can provide insights into outcomes expected more widely in response to global warming induced sea-level rise.

0 0

Post a comment