As seaweed forests are diminishing globally at a rate far exceeding their restoration, undermining the potential of this approach as a natural solution for removing carbon dioxide, according to a study published in the PLOS Biology.
The researchers, led by Karen Filbee-Dexter, from the University of Western Australia, analyzed published data on the evolution of kelp forest areas in different regions of the world, seeking to estimate the net impact of these changes on the capacity to sequester carbon.
The results show that the decline of kelp forests — the most widespread and productive seaweed ecosystem — could reduce natural carbon sequestration by between 1.5 and 30 million tonnes per year. This loss is between one thousand and ten thousand times larger than the annual increase in carbon dioxide sequestration achieved so far through kelp forest restoration projects.
The researchers estimate that, by 2050, climate change could cause the loss of around 25 million hectares of natural kelp forests. The area is more than 6,000 times the area restored since 1958.
Large kelp restoration projects undertaken in Norway and California required substantial investments of time, money and resources. According to the authors, tens of thousands of similar initiatives would be needed to compensate for losses caused by climate change, with costs that could reach tens or even hundreds of billions of dollars.
Protecting is more effective than restoring
Natural ecosystems have played an important role in reducing greenhouse gas emissions by absorbing carbon dioxide. However, the climate changes themselves are now compromising this capacity.
The restoration and planting of kelp forests is often presented as a natural climate solution due to the ability of these plants to sequester carbon and store it in the depths of the ocean. However, the researchers warn that the scale of losses caused by global warming makes this strategy insufficient to compensate for the disappearance of natural habitats.
“Conserving and restoring kelp forests is important, but we need to be realistic about what can be achieved in terms of significant mitigation of climate change through the removal of carbon dioxide,” the authors say.
They add that, currently, losses of kelp forests caused by climate change are several orders of magnitude greater than the gains achieved through restoration.
The researchers therefore argue that protecting threatened kelp habitats should be a priority. Preventing the loss of these ecosystems is, according to the study, a cheaper and more effective strategy than trying to restore them after destruction.
The authors also warn that presenting kelp forest restoration as a solution to remove carbon dioxide could create a false sense of security and delay essential measures, such as the reduction and gradual elimination of fossil fuel use.
“We argue that kelp forest restoration cannot provide a meaningful mitigation of climate change at the scale and speed required to offset the growth of our emissions,” they conclude.
