Data from: Species richness change across spatial scales

Humans have elevated global extinction rates and thus lowered global-scale
species richness. However, there is no a priori reason to expect that
losses of global species richness should always, or even often, trickle
down to losses of species richness at regional and local scales, even
though this relationship is often assumed. Here, we show that scale can
modulate our estimates of species richness change through time in the face
of anthropogenic pressures, but not in a unidirectional way. Instead, the
magnitude of species richness change through time can increase, decrease,
reverse, or be unimodal across spatial scales. Using several case studies,
we show different forms of scale-dependent richness change through time in
the face of anthropogenic pressures. For example, Central American corals
show a homogenization pattern, where small scale richness is largely
unchanged through time, while larger scale richness change is highly
negative. Alternatively, birds in North America showed a differentiation
effect, where species richness was again largely unchanged through time at
small scales, but was more positive at larger scales. Finally, we collated
data from a heterogeneous set of studies of different taxa measured
through time from sites ranging from small plots to entire continents, and
found highly variable patterns that nevertheless imply complex
scale-dependence in several taxa. In summary, understanding how
biodiversity is changing in the Anthropocene requires an explicit
recognition of the influence of spatial scale, and we conclude with some
recommendations for how to better incorporate scale into our estimates of
change.