USA: Ecosystems have shifted

Egkoregimes the Great Plains have wandered up to 590 kilometers to the north

The Great Plains form a north-south stripe in the center of the USA. Here, the ecosystems have shifted strongly northwards over the past 50 years. © NASA
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Creeping displacement: The Great Plains ecosystems have shifted significantly north over the past 50 years, as a study of bird populations reveals. At the southern edge, researchers identified a northward shift of about 260 kilometers, and in the north even more than 590 kilometers north. Causes are climate change, but also other human interference with nature, according to the scientists in the journal Nature Climate Change.

Scientists have been predicting for some time that climate change will lead to a shift in climate zones - and in some areas this is already detectable. Thus, the tropical belt has already grown by 0.5 degrees of latitude and the tracks of hurricanes reach further north. In the US, the rather dry climatic zone in the west of the country moves further and further to the east and has already passed the 100th longitude.

Northward migration of three Great Plains ecosystems. © University of Nebraska-Lincoln

Shift towards pole

Another example of shifting climate and eco-zones has now been discovered by Caleb Roberts of the University of Nebraska-Lincoln and his team in the United States. For their study, they had evaluated 50 years of data on the distribution and distribution of various bird communities in the Great Plains the approximately 500-kilometer-wide strip of poor-wood, rather dry field and grasslands in the Midwestern United States.

The result: The Great Plains ecosystems characterized by the various bird communities have shifted measurably to the north since 1970. "The analyzes revealed polynomial shifts in both the southern and northern koregime borders, " the researchers report. "This supports our hypothesis of a directional and relatively orderly migration."

Effect stronger in the north

The northern border of the grassland ecosystems has moved particularly quickly: over the past 50 years, it has drifted more than 50 kilometers farther this corresponds to an average of around 13 kilometers per year, as did Roberts and his team determined. By contrast, the southern borders of this koregimes moved much slower they have moved "only" 260 kilometers to the north. display

"These differences fit the expected phenomenon of arctic amplification, " explain the scientists. This term summarizes the effects of the polarization of climate change. Because, for example, the Arctic and the higher latitudes heat up more strongly in relation to the global average, the northern climate zones and ecosystems are also reacting more strongly.

The cause is climate change - but not only

But the cause for these ecosystem shifts is not climate change alone, as the researchers emphasize: "Like so many in ecology, these shifts have several causes, " says Roberts colleague Craig Allen, "It is almost impossible, for example, to separate the spread of the forest from climate change, because both are closely linked."

In addition to the climate change, the scientists see, among other things, changed, further north shifted bush and forest fire risk zones, land use by humans and also the increasing foresting of parts of the once more steppe-like landscape. For the grasslands, one of the most threatened zones in the world, this development is fatal, according to the researchers.

Conservation needs to adapt

"We are reaching the limit of grassland resilience, " warns Roberts. "It is on the verge of collapsing, especially in our region." The new findings may now help to better protect the Great Plains ecosystems. If the shift continues, many valuable and rare species communities could migrate out of the previous protected areas. If these are not adjusted, the protection remains ineffective. (Nature Climate Change, 2019; doi: 10.1038 / s41558-019-0517-6)

Source: University of Nebraska-Lincoln

- Nadja Podbregar