As coastal cities prepare for rising waters, they should keep in mind that sometimes natural solutions can be the most effective.
In a recent study, researchers found that coral reefs could dramatically decrease the effects of waves and storm surges made worse by climate change. In fact, they cut down on wave energy—a measure of the energy transferred in the ocean from wind to waves—by 97% At $1,290 per meter for restoration projects, coral is also significantly cheaper than other forms of protection, like artificial breakwaters, which break down to a cost of $19,791 per meter.
The study, published in Nature, is the first to look at how coral reefs can contribute to climate change mitigation and adaptation across the world's oceans. The researchers used data from 255 studies that gauged the link between coral reefs in the Atlantic, Pacific, and Indian Oceans and reductions in wave energy.
The three reef environments they analyzed—reef flat, reef crest, and whole reef—were all effective, with each dissipating 65% of wave energy, 86% of wave energy and 97% of wave energy respectively. They each also dramatically cut down on wave height.
While the researchers found that coral reef restoration is cheaper to implement than artificial protections against rising tides, they admit that a full cost-benefit analysis is still needed.
As living structures, reefs have the potential for self-repair and thus lower maintenance costs as compared with artificial structures, but reef restoration is still a comparatively new field. Most measures of reef restoration projects are limited to just the time period in which a project is constructed (that is, one funding cycle) particularly in developing countries where most reef restoration occurs. The addition of ecosystem benefits and considerations of maintenance costs in a full benefit:cost analysis would likely add to the relative cost effectiveness of reefs for coastal defence.
Maddeningly enough, coral reefs are deeply threatened by climate change. So in addition to restoration, anyone concerned about the future of coastal cities also needs to think about coral reef conservation.