Final Report Summary - GLOBEPURE (Global drivers of loss of biodiversity with eutrophication and their potential use for restoration ecology)
There is mounting evidence that human-driven global changes, including nutrient enrichment, impact many aspects of Earth’s ecosystem, especially productivity, stability and biodiversity. The GLOBEPURE project was dedicated to determine the consequences of changes in plant diversity on the functioning of ecosystems and the stable provision of ecological services. To deliver these objectives, the project used an ongoing globally replicated experimental network – Nutrient Network – manipulating three key nutrients (nitrogen, phosphorous and potassium) at more than 70 grassland sites around the world; as well as 12 long-term grassland field experiments performed at a single site – the Cedar Creek Ecosystem Science Reserve, Bethel, MN – manipulating some of the major global environmental changes.
The GLOBEPURE project first determined the extent to which natural gradients of diversity influence the stability of grassland ecosystems. It revealed that plant diversity can have a stabilizing effect on the productivity of natural grasslands (Fig. 1a). In other words, plant productivity was less variable when plant diversity was higher. This result mirrors those from biodiversity experiments that manipulate plant diversity while controlling for potentially confounding factors. But we bring the first demonstration that natural gradients of diversity have similar impact on grassland stability than experimentally manipulated gradient of diversity. The stabilizing effect of diversity came in part from asynchronous fluctuations in the biomass of different species across time (Fig. 1b). This is because the declines in the biomass of some species was more likely to be compensated for by increases in other species when the species pool was larger and more diverse, thus buffering temporal fluctuation in the productivity of the whole community. Furthermore, the project indicated that this stabilizing effect of diversity was weakened in comparable plant communities after they were fertilized (Fig. 2c). The weakening of the relationship between diversity and stability was due to increased temporal variation of plant productivity in diverse communities and decreased species asynchrony in high-diversity communities (Fig. 2d). In other words, the work showed that diverse ecosystems are more stable through time and that fertilization might cancel out the stabilizing effect of biodiversity (Hautier et al. 2014). It therefore emphasizes the threat of fertilization to the stable provisioning of ecosystem services. This is of major impact as ecosystems are undergoing dramatic changes due to anthropogenic influences that are affecting ecosystem functioning and human well-being.
GLOBEPURE also determined the extent to which changes in plant diversity in response to global environmental changes affect the stability of grassland ecosystems. We found that changes in plant diversity in response to important anthropogenic drivers including changes in nitrogen, carbon dioxide, fire, herbivory and water have strong influence on the stability of grassland productivity (all colored lines except red in Fig. 2). Furthermore, we found that the loss of plant diversity was associated with decreased stability both in experiments that manipulate diversity (red line in Fig. 2) and when biodiversity changed in response to other anthropogenic drivers. These findings suggest that any drivers of environmental change that affect biodiversity are likely to have long-term ecosystem impacts that result from these changes in biodiversity. Altogether, our multiyear experiments suggest that there may be a universal impact of biodiversity change on ecosystem stability in response to anthropogenic environmental changes, with decreased plant species numbers leading to lower ecosystem stability regardless of the cause of biodiversity loss (Hautier et al. 2015). This work suggests that conservation policies should encourage management procedures that restore or maintain natural levels of biodiversity or minimize the negative impacts of anthropogenic global environmental changes on biodiversity loss to ensure the stable provision of ecosystem services.
The project finally assessed whether plant diversity ensures the simultaneous provisioning of multiple ecosystem services at multiple spatial scales. It indicates that at small scales within sites, different species supported different processes at different spatial blocks, resulting in a greater number of species supporting ecosystem functioning when a wider range of processes and places were considered (Fig. 3). Across 65 grassland sites, higher plant diversity, measured at the alpha (number of species per plot within spatial blocks), beta (dissimilarities in species between plots within spatial blocks), and gamma (the total number of unique species among all plots within spatial blocks) scales, was associated with higher number of processes that achieve a high functional threshold for each process (Fig. 4). This work emphasize the importance of plant diversity to ensure the simultaneous provisioning of multiple ecosystem services at multiple spatial scales.
Hautier, Y., E. W. Seabloom, E. T. Borer, P. B. Adler, W. S. Harpole, H. Hillebrand, E. M. Lind, A. S. MacDougall, C. J. Stevens, J. D. Bakker, Y. M. Buckley, C. Chu, S. L. Collins, P. Daleo, E. I. Damschen, K. F. Davies, P. A. Fay, J. Firn, D. S. Gruner, V. L. Jin, J. A. Klein, J. M. H. Knops, K. J. La Pierre, W. Li, R. L. McCulley, B. A. Melbourne, J. L. Moore, L. R. O'Halloran, S. M. Prober, A. C. Risch, M. Sankaran, M. Schuetz, and A. Hector. 2014. Eutrophication weakens stabilizing effects of diversity in natural grasslands. Nature 508:521-+.
Hautier, Y., D. Tilman, F. Isbell, E. W. Seabloom, E. T. Borer, and P. B. Reich. 2015. Anthropogenic environmental changes affect ecosystem stability via biodiversity. Science 348:336-340.
The GLOBEPURE project first determined the extent to which natural gradients of diversity influence the stability of grassland ecosystems. It revealed that plant diversity can have a stabilizing effect on the productivity of natural grasslands (Fig. 1a). In other words, plant productivity was less variable when plant diversity was higher. This result mirrors those from biodiversity experiments that manipulate plant diversity while controlling for potentially confounding factors. But we bring the first demonstration that natural gradients of diversity have similar impact on grassland stability than experimentally manipulated gradient of diversity. The stabilizing effect of diversity came in part from asynchronous fluctuations in the biomass of different species across time (Fig. 1b). This is because the declines in the biomass of some species was more likely to be compensated for by increases in other species when the species pool was larger and more diverse, thus buffering temporal fluctuation in the productivity of the whole community. Furthermore, the project indicated that this stabilizing effect of diversity was weakened in comparable plant communities after they were fertilized (Fig. 2c). The weakening of the relationship between diversity and stability was due to increased temporal variation of plant productivity in diverse communities and decreased species asynchrony in high-diversity communities (Fig. 2d). In other words, the work showed that diverse ecosystems are more stable through time and that fertilization might cancel out the stabilizing effect of biodiversity (Hautier et al. 2014). It therefore emphasizes the threat of fertilization to the stable provisioning of ecosystem services. This is of major impact as ecosystems are undergoing dramatic changes due to anthropogenic influences that are affecting ecosystem functioning and human well-being.
GLOBEPURE also determined the extent to which changes in plant diversity in response to global environmental changes affect the stability of grassland ecosystems. We found that changes in plant diversity in response to important anthropogenic drivers including changes in nitrogen, carbon dioxide, fire, herbivory and water have strong influence on the stability of grassland productivity (all colored lines except red in Fig. 2). Furthermore, we found that the loss of plant diversity was associated with decreased stability both in experiments that manipulate diversity (red line in Fig. 2) and when biodiversity changed in response to other anthropogenic drivers. These findings suggest that any drivers of environmental change that affect biodiversity are likely to have long-term ecosystem impacts that result from these changes in biodiversity. Altogether, our multiyear experiments suggest that there may be a universal impact of biodiversity change on ecosystem stability in response to anthropogenic environmental changes, with decreased plant species numbers leading to lower ecosystem stability regardless of the cause of biodiversity loss (Hautier et al. 2015). This work suggests that conservation policies should encourage management procedures that restore or maintain natural levels of biodiversity or minimize the negative impacts of anthropogenic global environmental changes on biodiversity loss to ensure the stable provision of ecosystem services.
The project finally assessed whether plant diversity ensures the simultaneous provisioning of multiple ecosystem services at multiple spatial scales. It indicates that at small scales within sites, different species supported different processes at different spatial blocks, resulting in a greater number of species supporting ecosystem functioning when a wider range of processes and places were considered (Fig. 3). Across 65 grassland sites, higher plant diversity, measured at the alpha (number of species per plot within spatial blocks), beta (dissimilarities in species between plots within spatial blocks), and gamma (the total number of unique species among all plots within spatial blocks) scales, was associated with higher number of processes that achieve a high functional threshold for each process (Fig. 4). This work emphasize the importance of plant diversity to ensure the simultaneous provisioning of multiple ecosystem services at multiple spatial scales.
Hautier, Y., E. W. Seabloom, E. T. Borer, P. B. Adler, W. S. Harpole, H. Hillebrand, E. M. Lind, A. S. MacDougall, C. J. Stevens, J. D. Bakker, Y. M. Buckley, C. Chu, S. L. Collins, P. Daleo, E. I. Damschen, K. F. Davies, P. A. Fay, J. Firn, D. S. Gruner, V. L. Jin, J. A. Klein, J. M. H. Knops, K. J. La Pierre, W. Li, R. L. McCulley, B. A. Melbourne, J. L. Moore, L. R. O'Halloran, S. M. Prober, A. C. Risch, M. Sankaran, M. Schuetz, and A. Hector. 2014. Eutrophication weakens stabilizing effects of diversity in natural grasslands. Nature 508:521-+.
Hautier, Y., D. Tilman, F. Isbell, E. W. Seabloom, E. T. Borer, and P. B. Reich. 2015. Anthropogenic environmental changes affect ecosystem stability via biodiversity. Science 348:336-340.