The number of stressors operating above high levels is an important independent factor for multiple services when compared to individual stressors. Relative importance of the multistressors index (number of stressors exceeding a certain threshold) compared to single factors for assessing multiple services. aA qualitative assessment of variable significance by demonstrating results from a multi-model inference approach. Lists of the best generalized linear models of all possible combinations of environmental pressures for world #1a and global #2 are presented. R2s of saturated models (the ones from which variable significance was calculated) were 0.3834 for world #1 and 0.5905 for world #2. If the variable(s) are included in the model (significant), this is shown with a colored box (green for multiple factors, red for single stresses climate, blue for soil-related stresses and yellow for other forms of human impact). Effect sizes for each variable can be seen in Supplementary Table 6. Bayesian information criterion (BIC) indicates fit of the model (the lower the better) and delta indicates the difference of the BIC with respect to the best model (<4 indicates similar performance to the best model ). The weight of the models is also represented in the table and indicates how each of the best models contributes to an average model (results in Supplementary Table 7). B, a quantitative assessment of variable significance using a split-variance system. Pie charts indicate the percentage of variance explained for multiple services (R2) associated with each predictor. credit: The nature of climate change (2023). DOI: 10.1038/s41558-023-01627-2
Through statistical analysis of data from around the world, scientists have determined that multiple natural and human stressors reduce levels of biodiversity and soil functioning in soil ecosystems. The number and specific composition of these stresses are determining factors in this interaction. This is the conclusion reached by an international team of scientists led by Matthias C. Rillig, professor of biology at Freie Universität.
The results of their study have now been published in The nature of climate changeentitled “Increasing number of stressors reduces soil ecosystem services worldwide.”
To survive, soils and terrestrial ecosystems around the world must deal with a wide range of natural and human pressures. These include droughts, warming, and exposure to harmful chemicals, including microplastics. Not only the type of stresses, but also their number (in particular, those caused by human activity) have a negative impact on various processes in the soil.
“Our previous laboratory studies showed that an increasing number of global change agents led to a decrease in soil processes such as decomposition, soil aggregation, and soil respiration, as well as a decrease in soil biodiversity,” says Professor Relig, lead author of the study and head of the research team, which also included a scientist Spanish environmentalist Dr. Manuel Delgado Baquerizo.
The research team analyzed two standardized global field surveys of soils and a combination of natural and human factors known to influence soil ecosystems.
“Our study assessed soil ecosystems by classifying fifteen ecosystem variables into six major types of ecosystem services: decomposition of organic matter, soil biodiversity, pathogen control, plant productivity, water regulation, and nutrient cycling. For the purposes of the study, we defined Seven important environmental variables as stressors.They were selected based on their potential to create environmental stressors when they reach high levels: drought, temperature, seasonality, salinity, distance from neutral pH, levels of heavy metals, and human influence.We also took the level of pesticides and microplastics in soils, as data was available on these for a subset of sites in one of the global field surveys,” explains Relig.
In order to investigate the number of stressors as parameters in the study, data from global field surveys must first be converted into a variable that reflects the number of factors. To do this, the researchers counted the number of environmental stressors that exceeded a certain threshold value.
The number of stressors was considered to have exceeded a threshold when it exceeded 75 percent of the maximum stress levels. The investigation showed that increasing the number of factors above a certain threshold reduced the ability of soils to support ecosystem services.
“This increased number of stresses beyond a threshold could explain soil interactions that, until now, could not be attributed to the type of stressors alone,” Relig says. In addition, the results of the study showed that “human beings should reduce their impact on ecosystems by reducing the number of factors that negatively affect soil processes and soil biodiversity.”
The mixture of human influences collectively affects soil processes and soil ecosystem biodiversity. “If the extent of this problem is not reduced, that is, the number of stressors that exceed a critical threshold, we risk losing important ecosystem services,” says Relig.
At the same time, Relig notes, the study primarily took an observational approach. This means that the researchers were able to detect patterns but could not draw any direct conclusions regarding causation. More research will be needed to explain the relationship between the number of stressors and ecosystem response. The effects of multiple concurrent factors on other types of ecosystems (for example, aquatic systems) could provide a potential avenue for future study.
more information:
Matthias C. Relig et al., An increasing number of stressors reduce soil ecosystem services worldwide, The nature of climate change (2023). DOI: 10.1038/s41558-023-01627-2
the quote: Global Analysis Shows Soil Ecosystems Under Stress (2023, March 28) Retrieved March 28, 2023 from https://phys.org/news/2023-03-global-analysis-soil-ecosystems-stress.html
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