Agriculture transforms entire ecosystems

A research team studied the effects of agricultural grassland use on communities of organisms. Their study, recently published in the journal Natural communicationsreveals for the first time that measures such as fertilization and mowing affect organisms at all levels of an ecosystem and throughout the food chain, thereby speeding up the entire system.

Everywhere in nature, living organisms are adapted to the conditions of their habitat. Depending on the environment, they rely on strategies of fast or slow growth, larger or smaller body size, and they reproduce at different rates. Two factors are decisive in this regard: the availability of nutrients and the extent of “disturbing” external influences.

“You can visualize this as the fable of the hare and the tortoise, except that, depending on the environment, the ‘race’ is sometimes ‘won’ by organisms with one strategy and sometimes by those following the other,” explains Professor Dr. Peter Manning from the Senckenberg Biodiversity and Climate Research Center in Frankfurt, who led the research team alongside Dr. Margot Neyret from the University of Grenoble Alpes.

“In undisturbed, nutrient-poor ecosystems, slower organisms – ‘turtles’ – predominate. They use their resources more sparingly, grow more slowly and reproduce less frequently, but they are generally larger and live longer long. In contrast, under species-rich conditions, the quicker the “hares” come to the top: these organisms tend to be smaller and have a higher nutrient turnover, with a lower life expectancy and a rate of higher reproduction.

“In our study, we were able to show for the first time that intensive agricultural use of grasslands leads to ‘hares’ predominating at all levels of an ecosystem.”

In their study, the researchers analyzed a wealth of data collected as part of the Biodiversity Exploratories project for areas in the Swabian Alb, the Hainich region in central Germany and the Brandenburg biosphere reserve Schorfheide-Chorin.

“We examined organisms from all areas of the sampled ecosystems, from soil microorganisms to plants, butterflies and other arthropods, including birds and bats,” reports Neyret, a former research assistant. at SBiK-F.

“We were able to determine the effects of agricultural management in the form of fertilization, mowing and grazing for almost all organisms. Compared to unmanaged natural areas, organisms that follow the ‘grow fast, die young’ strategy dominated here – the entire ecosystem had become “faster” in these cases.

“This is partly due to the direct impact of the alteration of resources and environmental conditions and partly to indirect cascading effects within food chains. Depending on the intensity of use, the ecosystems studied are distributed along an axis from ‘slow’ to ‘fast.’ Only in a few larger animals and soil organisms have we been able to observe this effect.”

As the study shows, agricultural use also impacts various ecosystem functions carried out by organisms, which also become “faster”, depending on the intensity of cultivation. “In accelerated ecosystems, processes such as decomposition, biomass production or nutrient cycling, for example, also occur more quickly,” explains Manning.

“From a human perspective, such systems are initially more agriculturally productive and provide higher yields. However, this could reduce their ability to store carbon. At the same time, increased nutrient leaching results in higher levels of pollution. Undisturbed natural ecosystems, on the other hand, tend to have a higher level of biodiversity and are more resilient. This also plays a role with regard to the increase in extreme weather events linked to climate.

Neyret adds: “As a result of increasingly intensive agriculture, we are likely accelerating ecosystems worldwide. We know from other studies that it is relatively easy to speed up an ecosystem using fertilizer, but returning it to its original “slow” state takes a long time. We are thus losing more and more slow systems with their specific organisms and functions. In the interests of diversity – and also taking into account the challenges posed by climate change – countermeasures are urgently needed in this regard.