Posted: March 27, 2020

Recently, a debate has developed over how biodiversity is changing at different spatial scales across the planet.

While most researchers agree species extinctions are increasing globally due to human activity, several research groups have recently begun to argue that species richness at local spatial scales is not declining as many biologists have claimed. The basis of this argument stems from analyses of biological monitoring programs and time-series data that suggest species richness is decreasing in some locations, increasing in others, but not changing on average.

Brad Cardinale and many of his colleagues have argued that time-series datasets give a misleading picture of how biodiversity is changing across the planet for at least three reasons:

First, time-series data rarely account for habitat loss, the world's primary driver of biodiversity loss. Since 1700, 75% of land has been transformed by human activities, including 57-million km2 of natural habitat that has been converted to agriculture and urban environments. Yet, because biologists do not typically monitor biodiversity before and after conversion of natural habitats to cornfields, clear-cut forests, or parking lots, BioTIME fails to capture the pervasive impacts of habitat loss on biodiversity.

Second, time-series datasets are heavily biased towards monitoring programs in rich nations in North America and Europe, with sparse data from developing nations and tropical locations where the majority of biodiversity exists.

Third, because most of the analyzed time series are of short duration (< 16 years) and limited to the last few decades, the time spans under-represent human impacts on biodiversity in the surveyed locations.

These points, and others, have been developed in a set of papers that have critiqued the rigor of conclusions about biodiversity change that are based on time-series data:

Cardinale et al. 2018. "Is local biodiversity declining or not? A summary of the debate over analysis of species richness time trends. Biological Conservation, 219:175-183"

Gonzalez et al. 2016. "Estimating local biodiversity change: A critique of papers claiming no net loss of local diversity. Ecology, 98:1949-1960"

Check out the story about the debate in YaleEnvironment360

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