Climate change is in the eyes of many synonymous with global warming. One predicted consequence of global warming is a gradual poleward drift of animals and plants as their existing environments become uncomfortably hot and dry. Our climate is changing, but the simple picture of warming and migration can mask the real-world complexity of climate change, which occurs at different rates in different places, with variations between ocean and land, plain and mountain, desert and forest.
Scottish Marine Institute ecologist Michael Burrows, together with colleagues in eight other countries, has been looking in detail at variations in climate change over time and place. Using global temperature records spanning the past 50 years, the researchers have found that the impacts of climate change on ocean and land organisms are comparable, and have shown that local changes can deviate from the anticipated poleward expansion and earlier onset of spring.
In a study published in the journal Science, Burrows and his colleagues look at the velocity of climate change – geographic shifts of equal temperature contours over time – and changes in seasonal onset. Both measures are higher in the ocean than on land, despite the greater capacity of water over soil and rocks to absorb heat. This has consequences for conservation, as areas with a high degree of marine biodiversity are subject to more potentially damaging effects from rapid climate change.
When it comes to the magnitude of climate change velocity, we have seen average range shifts of more than 16 kilometres per decade, for a combination of land and marine species, with the onset of spring advancing by two and a half days per decade on land, and more than four days per decade at sea. But these are global averages, and the wide spread in numbers reported is due to the dynamic and diverse patterns of climate change across the planet. For example, the velocity of climate change is two to seven times faster in the ocean than on land at the sub-Arctic latitudes inhabited by Britain and southern Scandinavia, and also within 15 degrees of the equator. Elsewhere, the ocean-landmass difference is small.
Animals and plants will migrate to more habitable regions, but this is not always possible. Boundaries between land and ocean can constrain the movement of species, as in the Mediterranean, cutting off possible escape routes. The overall result is that habitat-specific patterns in temperature may run counter to the expected poleward migration and shift toward an earlier spring and later autumn.
Climate change and shifting seasons threaten biodiversity, and an understanding of the local and regional complexity of climate change is essential if we are to mitigate its effects on the world’s diverse and often highly sensitive ecosystems. Evolution shows us how organisms adapt to their environment, but plants and animals are limited in the degree to which they can cope with rapid climate change.
The work of Michael Burrows and his colleagues provides a basis for a detailed understanding of local and regional climate complexity, and its effect on terrestrial ecosystems, and will be used to generate predictions for comparison with observed biological change.
Burrows et al., “The pace of shifting climate in marine and terrestrial ecosystems”, Science 334, 652 (2011)