地球温暖化を放置すれば過去300万年間になかったような海洋生態系の変化が起こるかもしれない

Moderate warming - driven by a greenhouse-gas emissions scenario that stabilizes around 2040 - could cause major reorganizations of marine biodiversity over large oceanic regions by the end of the century, suggests a study published online this week in Nature Climate Change. These changes, such as local species extinctions and species invasions, may be three times greater than those observed over the past 50 years.

Gregory Beaugrand and colleagues modelled patterns of marine biodiversity up to the end of the twenty-first century under different emissions and associated warming scenarios. They then compared these potential future patterns of biodiversity with those seen between 1960 and 2013, as well as during two periods of Earth’s history with climates very different from today: the peak of the last ice age, the Last Glacial Maximum, (LGM), which lasted from around 26,500 to 20,000 years ago; and the mid-Pliocene, a relatively warm period ending around 3 million years ago.

The researchers project that severe global warming driven by continued growth in greenhouse-gas emissions to 2100 would have a major effect on oceanic ecosystems, with between 50 and 70% of the world’s oceans experiencing a change in marine biodiversity similar to or higher than that experienced between the LGM or mid-Pliocene and today. However, if global warming is relatively small due to emissions peaking and then declining within the next 5 years, the study suggests that biological changes would be much less dramatic and not that different from annual variability seen since the 1960s. Nevertheless, any reorganization is likely to affect ecosystem functioning, underscoring the need to better understand the effects of climate change on patterns of biodiversity.