To summarize, climate crisis is the defining issue of the century. Buildup of anthropogenic greenhouse gases (GHGs) in Earth’s atmosphere is driving global heating, while a convergence of global crises threatens to rupture key planetary boundaries. Although the human activities which drive these converging crises (for simplicity: the climate crisis) are diverse and complex, the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) breaks down the sources of anthropogenic GHG emissions into five high-level sectors. Similarly, the impacts of climate crisis – in their variety and complexity – are almost impossible for an individual to grasp, but so far, this sub-series has covered: global heating, Arctic amplification, heat waves, droughts and floods, disruption of oceanic and atmospheric patterns, cryosphere collapse, declining oceanic dissolved oxygen content, sea level rise, and fisheries collapse. In the absence of dramatic global climate action this decade, climate crisis will likely spiral out of control, rupturing key planetary boundaries and endangering the future of organized human life on Earth.
Today’s post centers the risk posed to coral reefs from the combination of warming, acidification, and deoxygenation of the oceans. To quote from Chapter 3 of the IPCC’s “Special Report: Global Warming of 1.5ºC“: “Even achieving emissions reduction targets consistent with the ambitious goal of 1.5°C of global warming under the Paris Agreement will result in the further loss of 70–90% of reef-building corals compared to today, with 99% of corals being lost under warming of 2°C or more above the pre-industrial period.” So the struggle (at this point against all odds) to limit warming to 1.5ºC is a struggle to preserve something like 10 to 30% of extant coral reefs, whereas, should warming reach 2ºC, the IPCC predicts 1% or less of existing reefs will survive. Given that these are some of the most diverse and productive ecosystems on the planet and anchors of many marine food chains, the ecological and economic impacts (before even factoring in tourism) of such reef losses stand to be immense, but there is also the profound tragedy of human (as always, read: largely corporate) actions leading to the destruction of something so vital and beautiful. Through our collective action (and inaction), we are impoverishing the Earth.
For readers interested in going deeper on the sensitivity of corals to threats under climate crisis, here’s a recent Nature Climate Change article that I found really interesting. And for all, here’s a little of what AR5 had to say about coral: