Ecosystems in marine protected areas are still at risk from greenhouse gas emissions, reports a paper published online this week in Nature Climate Change. The study shows that by 2050, 42% of areas with fishing bans will be exposed to warming waters and decreasing oxygen levels that exceed natural variability.
John Bruno and colleagues investigate 8,263 marine protected areas across the globe, including 309 areas where fishing is banned. They model sea surface temperatures and oxygen concentrations at both moderate and high emissions scenarios, to predict the impact on protected ecosystems. From this, they calculate a ‘community thermal safety margin’ (CTSM) for each ecosystem, which is - for all species present - the average of the margin between each species’ temperature tolerance and the local maximum temperature. Exceeding the CTSM could lead to substantial loss of biodiversity
The authors show that marine protected areas are predicted to warm at a similar rate as unprotected areas, with the exception of the polar regions. The tropics will be the first to exceed the CTSM by about 2050, with temperate latitudes following by around 2150.
This study highlights how the emergence of ecosystem stressors differs between regions, so shifting protected areas due to one stressor may result in exposure to another.