Biotic Homogenization in Freshwater Ecosystems

Biotic homogenization in freshwater ecosystems describes the progressive loss of distinctiveness among aquatic communities, whereby local assemblages become increasingly similar in taxonomic, functional and phylogenetic composition. This phenomenon is driven by a suite of anthropogenic pressures—most notably the introduction of non-native species, habitat alteration through damming or channel modification, pollution and landscape connectivity changes. As local (alpha) diversity may rise with the arrival of widespread generalists, regional (gamma) diversity often declines, leading to reduced differentiation (beta diversity) among sites. The homogenization of ecological traits can impair ecosystem functioning, undermine resilience to disturbance and erode the unique biotic character of freshwater habitats. Globally, rivers, lakes and wetlands exhibit uneven patterns of homogenization, reflecting the interaction of land-use intensity, climatic shifts and historical biogeography. Understanding the mechanisms by which species invasions, environmental filtering and trophic reorganisation jointly shape community similarity is critical to inform conservation strategies aimed at preserving both local biodiversity and the distinctiveness of regional faunas.

Research from Nature Portfolio

Recent studies have revealed that riverine fish communities can undergo rapid compositional change, averaging around 30% turnover per decade, accompanied by increases in total abundance and species richness. These shifts are largely mediated by the timing and intensity of anthropogenic pressures, with non-native species introductions playing a compensatory role by offsetting declines in native richness and abundance. Such dynamics underscore the complex balance between species loss and gain, and highlight that homogenization may mask ongoing biodiversity change. Another investigation into Mediterranean stream ecosystems has shown that high degrees of exotic species invasion correlate with lower functional diversity. Invading species often possess narrower trait repertoires than natives, leading to simplified trait distributions within communities. Environmental factors such as altitude and stream order influence both native and non-native functional patterns, but invasions can override key drivers, resulting in reduced ecological redundancy and altered ecosystem processes.

Biotic Homogenization in Freshwater Ecosystems publication trend

The graph below shows the total number of articles in biotic homogenization in freshwater ecosystems across all publications each year (not limited to Nature Index journals).

Technical terms

Alpha diversity: number of species within a single site or community.

Beta diversity: variation in species composition among multiple sites.

Gamma diversity: total species richness across a larger region encompassing multiple communities.

Biotic homogenization: decrease in beta diversity over time, leading to similar community composition across sites.

Functional diversity: range and relative abundance of species’ ecological traits within a community.

Non-native species: organisms introduced outside their historical range by human action.

References

1. Biotic homogenisation and differentiation as directional change in beta diversity: synthesising driver–response relationships to develop conceptual models across ecosystems. Biological Reviews (2023).
2. Past and recent anthropogenic pressures drive rapid changes in riverine fish communities. Nature Ecology & Evolution (2024).
3. Exotic species invasions undermine regional functional diversity of freshwater fish. Scientific Reports (2019).