Does increasing human environmental footprint lead to biotic
homogenization of forest bird communities in northern USA?
Abstract
Studies have shown negative impacts of increased human pressures on
biodiversity at local (alpha-diversity) and regional (gamma-diversity)
scales. However, the diversity between local sites (beta-diversity) has
received less attention. This is an important shortcoming since
beta-diversity acts as a linkage between trends at the local and
regional scales. Decreased beta-diversity means that local sites lose
their distinctiveness, becoming more similar to each other. This
process, known as biotic homogenization, is predicted to arise through
the replacement of native specialists with native and non-native
generalists. However, the mechanisms causing biotic homogenization have
not been fully studied nor its impacts on different facets of
biodiversity. We examined if land-use change due to human actions causes
biotic homogenization of taxonomic, functional and phylogenetic
diversity in bird communities of forested habitats in the state of
Minnesota, USA. Our aim was to study if increased human pressure, which
included human population density, land transformation, transport
infrastructure, and electrical power infrastructure, was associated with
increased similarity among bird point count sites. Our results showed
that elevated human pressure was not related with increased biotic
homogenization in this study region. Interestingly, increased human
pressure appeared to increase the between-site functional diversity of
bird communities. This association was driven by a decrease in local
diversity, which, due to the nature of beta-diversity, led to an
increase in between-site diversity. We highlight the importance of
considering multiple facets of biodiversity and the use of
beta-diversity in a conservation setting.