May 15, 2018 — A paper (Bruno et al. 2018) released last week in Nature Climate Change mapped the effects of future emissions on marine protected areas (MPAs) around the world. The results were unsurprising—climate change threatens every MPA (and indeed every part of the ocean), with a range of impacts. This study focused mainly on warming temperatures and changing oxygen levels, but anthropogenic stressors on the ocean also include ocean acidification, rising sea levels, more intense storms, distorted currents, and altered nutrient distribution.

To understand the paper, its conclusions, and any kind of positive takeaway (we get there at the end), an understanding of representative concentration pathways (RCP) is needed. An RCP is a scientifically backed estimate of radiative forcing (you can think of this as the amount of global warming) based on different emissions scenarios. Basically, an RCP estimates the amount of warming Earth will experience based on the amount of future emissions. It is important to note that RCPs are not climate models—they are scientifically standardized scenarios that can be used to set up models. The 4 recognized RCPs are: RCP 2.6, 4.5, 6, and 8.5.

In the paper, the authors model RCP 8.5, the worst-case scenario where politicians, governments and people don’t make meaningful change in the future. Predictably, the results are not good. In this scenario, temperatures inside (and outside) MPAs are expected to rise by an average of 0.035° C per year leading to “protected areas” that are at least 2° C (4.6° F) warmer by the end of the century.

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