Humans Have Devastating Impact on Grassland Species

The common restharrow or Ononis repens is a host plant for the insect Macrotylus paykulli, which feeds on its sap. (Photo: Lars Skipper)
The common restharrow or Ononis repens is a host plant for the insect Macrotylus paykulli, which feeds on its sap. (Photo: Lars Skipper)

(CN) – Species ranging from single-celled organisms to vertebrates have certain habitat requirements or preferences that will ultimately be disrupted and lead to extinction in many cases, according to a study published Wednesday in the journal Nature.

Minor variations within fields – such as a reduced community of distinct plants – can impact species, either forcing them to move or die off, which affects organisms that rely on them as food sources.

“For the first time, we investigated all groups of species along the food chain on grasslands with different forms of land use in a variety of regions,” said lead author Martin Gossner of the Technical University of Munich, who helped coordinate data and research produced by 300 scientists studying the consequences of land-use intensification.

The scientists studied how land usage by humans – such as cutting grass – impacted 4,000 species, using a new statistical procedure that enabled them to track nonlinear effects on diversity of species communities between grassland areas on a gradient.

Their findings show that even minor land care by humans produced dramatic effects on the species observed.

“According to our observations, the homogenization of species does not progress proportionally to the intensity of use. Instead, even a moderate management of grassland results in cross-regional communities being reduced to the same, less demanding all-rounders,” Gossner said. “A further increase in the intensity of use simply doesn’t have a comparable effect.”

Such changes lead to the potential extinction of high-maintenance species such as the common restharrow, a host plant, and the Macrotylus paykulli, an insect that feeds on the restharrow’s sap and the occasional insect that gets caught in the plant’s glandular hairs. The Macrotylus paykulli relies on the common restharrow, so as the plant dies off, the insect loses its habitat and eventually goes extinct as well.

“What is new here is the finding that the homogenization of species takes place across landscapes, thereby reducing the diversity of species at a regional and national level,” Gossner said. “Which is probably a more significant consequence of the intensification of land use than the local loss of species alone.”

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