Abstract
There is high uncertainty surrounding the magnitude of current and future biodiversity loss that is occurring due to human disturbances. Here, we present a global meta-analysis of experimental and observational studies that report 327 measures of change in species richness between disturbed and undisturbed habitats across both terrestrial and aquatic biomes. On average, human-mediated disturbances lead to an 18.3% decline in species richness. Declines in species richness were highest for endotherms (33.2%), followed by producers (25.1%), and ectotherms (10.5%). Land-use change and species invasions had the largest impact on species richness resulting in a 24.8% and 23.7% decline, respectively, followed by habitat loss (14%), nutrient addition (8.2%), and increases in temperature (3.6%). Across all disturbances, declines in species richness were greater for terrestrial biomes (22.4%) than aquatic biomes (5.9%). In the tropics, habitat loss and land-use change had the largest impact on species richness, whereas in the boreal forest and Northern temperate forests, species invasions had the largest impact on species richness. Along with revealing trends in changes in species richness for different disturbances, biomes, and taxa, our results also identify critical knowledge gaps for predicting the effects of human disturbance on Earth's biomes.
Highlights
Developing the ability to predict the consequences of environmental change is one of the most significant challenges in ecology today (Chapin et al 1997; Pereira et al 2010; Dawson et al 2011)
On average, human disturbances lead to an 18.3% reduction (n = 327) in species richness (Fig. 2A)
This difference was more pronounced for species invasions, where experimental invasion studies had a lower decline in species richness losing an average of 11.2% less species (n = 16) than observational invasion studies, which lost an average of 24.2% of species (n = 116)
Summary
Developing the ability to predict the consequences of environmental change is one of the most significant challenges in ecology today (Chapin et al 1997; Pereira et al 2010; Dawson et al 2011). Given the increasing human domination of Earth’s biomes, establishing accurate estimates of the magnitude of biodiversity loss resulting from common human disturbances, such as landuse change and habitat loss, species invasions, climate change, and nutrient additions, is of particular importance. Potential time lags between environmental change and extinctions (Krauss et al 2010), differences in extinction rate estimates based on species-area-curves (He and Hubbell 2011), and other confounding effects have made predicting the magnitude of species loss resulting from various human-caused disturbances problematic (Bellard et al 2012). Differences between modeling approaches and uncertainties within model projections have resulted in widely varying predictions of future biodiversity change (Pereira et al 2010). Two modeling approaches used to project the future global extinction risks for birds revealed very different estimates with Jetz et al (2007) projecting 253–455 species at risk for extinction by the year 2100 while Sekercioglu et al (2008) projects 2150 species at risk for extinction in the same time period
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