The number of grasshoppers is decreasing in parallel with the decline in the quality of ecosystems such as grasslands: this was achieved by a study published in Proceedings of the National Academy of Sciences. The researchers conducted the study in a prairie in Arkansas analyzing data from the last two decades.
According to the researchers themselves, everything is due to increased levels of CO2 in the atmosphere that have decreased important nutrients such as nitrogen, phosphorus and sodium in plants, which in turn led to the decline of grasshoppers.
The study was carried out by Ellen Welti, researcher at the Geographical Ecology Group of the OU Department of Biology, in collaboration with other institutes.
“This decline in plant nutrient concentration represents a challenge for all plant consuming animals, including humans,” reveals the researcher.
This study confirms that many species of insects are declining in number and that grasshoppers are no less so despite the prairies of Arkansas, the environment taken into account for the study, represents a privileged stable habitat for these insects.
The decrease calculated by the researcher would be 2% per year over the last 20 years despite a doubling of plant biomass over the same period. The decrease in the number of grasshoppers can be explained by the lower quality of the plants in relation to the nutrients they can offer and the dilution of these nutrients.
“The greenhouse gas CO2 is warming the Earth and acidifying its oceans, but it is also the main ingredient of sugars, starches and cellulose in plants,” said Michael Kaspari, senior author of the study.
According to the researcher, human beings, by immersing more and more CO2 into the atmosphere, are also promoting the growth of more plants. However, without enough nutrients to fertilize all of these plants, the nutritional value of each plant is diluted and lowered. This means less and less quality food for grasshoppers.
According to the researchers, this is not a phenomenon limited to Arkansas: the dilution of plant nutrients is probably a global phenomenon and therefore a challenge for all herbivorous animal populations around the world.