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Research

INVESTIGATING CAUSES AND CONSEQUENCES OF CHANGES IN BIODIVERSITY

The Isbell Biodiversity Lab is investigating how biodiversity and ecosystem functioning respond to global environmental changes, such as land use changes, nutrient enrichment, exotic species introductions, and climate extremes. We also study the responses of ecosystem functioning, stability, and services to changes in biodiversity.


RESEARCH QUESTIONS

  • How do global environmental changes impact biodiversity and ecosystem functioning?
  • How do changes in biodiversity influence ecosystem functioning, stability, and services?

CURRENT PROJECTS

SELECTED PUBLICATIONS

Isbell et al. 2017 Nature

Here we review the recent literature and conclude that biodiversity loss substantially diminishes several ecosystem services by altering ecosystem functioning and stability, especially at the large temporal and spatial scales that are most relevant for policy and conservation. Biodiversity enhances many of nature’s benefits to people, including the regulation of climate and the production of wood in forests, livestock forage in grasslands, and fish in aquatic ecosystems. Yet people are now driving the sixth mass extinction event in Earth’s history. Human dependence and influence on biodiversity have mainly been studied separately and at contrasting scales of space and time, but new multiscale knowledge, which we review here, is beginning to link these relationships.


Isbell et al. 2015 Nature

Here we find that biodiversity increases the resistance of plant productivity to a broad range of climate events, including wet or dry, moderate or extreme, and brief or prolonged events. Specifically, the productivity of low-diversity communities with one or two grassland plant species changes by approximately 50% during climate events, whereas that of high- diversity communities with 16–32 species is more resistant, changing by only approximately 25%. By a year after each climate event, ecosystem productivity had often fully recovered, or over-shot, normal levels of productivity in both high- and low-diversity communities, leading to no detectable dependence of ecosystem resilience on biodiversity. Our results suggest that biodiversity mainly stabilizes ecosystem productivity, and productivity-dependent ecosystem services, by increasing resistance to climate events.


Isbell et al. 2015 Ecology Letters

Here we show that there is substantial value in conserving not only the quantity (area), but also the quality (biodiversity) of natural ecosystems for the sustainable provision of ecosystem services at a global scale. Biodiversity loss is likely creating an ecosystem service debt: a gradual loss of biodiversity-dependent benefits that people obtain from remaining fragments of natural ecosystems. In this paper, we develop an approach for quantifying global ecosystem service debts, and illustrate its use to estimate how one anthropogenic driver, habitat destruction, could indirectly diminish one ecosystem service, carbon storage, by creating an extinction debt. We estimate that approximately 2–21 Pg C could be gradually emitted globally in remaining ecosystem fragments because of plant species loss caused by nearby habitat destruction.


Isbell et al. 2013 Ecology Letters

Here we find that plant diversity can persist in a depauperate state for decades after cessation of nutrient enrichment. In our 30-year grassland experiment, plant diversity decreased well below control levels after 10 years of chronic high rates of nitrogen addition, and did not recover to control levels 20 years after nitrogen addition ceased. Furthermore, we found a hysteretic response of plant diversity to increases and subsequent decreases in soil nitrate concentrations. Our results suggest that chronic nutrient enrichment created an alternative low-diversity state that persisted despite decreases in soil nitrate after cessation of nitrogen addition, and despite supply of propagules from nearby high-diversity plots.


Isbell et al. 2013 PNAS

Here we find that the long-term impacts of anthropogenic drivers of environmental change on ecosystem functioning can strongly depend on how such drivers gradually decrease biodiversity and restructure communities. We found that although chronic nitrogen enrichment initially increased productivity, it also led to loss of plant species, including initially dominant species, which then caused substantial diminishing returns from nitrogen fertilization. In contrast, elevated CO2 did not decrease grassland plant diversity, and it consistently promoted productivity over time.


Isbell et al. 2011 Nature

Here we find that that although species may appear functionally redundant when one ecosystem function is considered under one set of environmental conditions, many species may still be needed to maintain ecosystem multifunctionality at multiple times and places in a changing world. Specifically, we find that 84% of the 147 grassland plant species studied in 17 biodiversity experiments promoted ecosystem functioning at least once. Different species promoted ecosystem functioning during different years, at different places, for different functions and under different environmental change scenarios.