Global Warming and Coral Reefs: From Mitigation to Geoengineering
Authors: M. James, C. Crabbe, LIRANS Institute for Research in the Applied Natural Sciences, Faculty of Creative Arts, Technologies and Science, University of Bedfordshire, Park Square, Luton, United Kingdom
Abstract: Although they make up only 0.2% in area of the marine environment, coral reefs are the most biodiverse ecosystems of the ocean, estimated to harbour around one third of all described marine species most of which are found nowhere else. Their intricate three dimensional landscapes promote elaborate adaptation, richly complex species interdependencies, and a fertile source of medically active compounds. Carbon dioxide concentrations in the atmosphere are now increasing at a rate unprecedented for at least 44.9 million years and are at c. 387ppm, a level not experienced on Earth for more than 20 million years. The thermal limits for reef-forming corals have already been exceeded at which coral reefs are a stable feature of the Earth‘s tropical marine ecosystems. This means that coral reefs have entered a phase of degradation in which their future survival is in serious jeopardy. As the concentration of greenhouse gases continues to increase in the atmosphere additional climate change phenomena will continue to impact on coral reefs. Currently, mitigation efforts are proving ineffectual in reducing anthropogenic CO2 emissions. Coral reefs are the most sensitive ecosystems on the planet to climate change, and here we review modelling a number of geoengineering options, and their potential influence on coral reefs. There are two categories of geoengineering, shortwave solar radiation management, and longwave carbon dioxide removal. The first set of techniques only reduce some, but not all, effects of climate change, while possibly creating other problems. They also do not affect CO2 levels and therefore fail to address the wider effects of rising CO2, including ocean acidification, important for coral reefs. Solar radiation is important to coral growth and survival, and solar radiation management is not in general appropriate for this ecosystem. Longwave carbon dioxide removal techniques address the root cause of climate change, rising CO2 concentrations, they have relatively low uncertainties and risks. They are worthy of further research and potential implementation, particularly carbon capture and storage, bio-char, and afforestation methods, alongside increased mitigation of atmospheric CO2 concentrations.