Print PageOne of questions for the impact of land-use disturbances on aquatic biodiversity is how big an effect size there is from each type of disturbances. Though land-use change is often considered as a local disturbance event, it is becoming a global environmental issue with cumulative ecosystem effects across geographic regions. Documenting worldwide biodiversity loss, diagnosing major causes, and finding potential solutions are a challenge, because few studies have compared the response of bioindicators, such as macroinvertebrate diversity, to different types of land-use disturbances. We report recent studies investigating the relationships of land-use, stream conditions, and benthic diversity in rivers located in different geographic regions, which are the Chilliwack River in coastal British Columbia, Canada, the East River in south China, and tributaries of the Colorado River in central Texas, USA. We analyzed three large data sets to determine the impacts of different land-use disturbances (forest harvesting, farmland change, and urbanization) along with other environmental variable changes on benthic biodiversity. We used total impervious area (TIA, % of total urban/rural areas within a catchment) or forest harvesting history to measure land-use disturbances. Using partial least squares projection to latent structures (PLS) modeling, we assessed relationships between multiple environmental variables and benthic communities.
Results/Conclusions
PLS models indicated that in the Chilliwack River (11 sites) the observed benthos diversity at previously logged sites was significantly lower than the model predicted. The benthos’ biomasses at previously logged sites were significantly lower than those at reference sites. A legacy of measurable forest harvesting impacts on invertebrate diversity was detected up to 40 years after logging at a catchment-scale.
The East River study (11 sites) showed that TIA was negatively related to The East River water quality index (ERWQI). PLS models showed that family richness and relative abundance of macroinvertebrates were negatively influenced by TIA and positively by ERWQI. Land-use disturbances severely degraded ecosystem integrity, and thereby reduced aquatic biodiversity in the East River.
PLS analysis of 38 watersheds in Austin revealed negative relationships between TIA and bioindicators (benthic macroinvertebrate and diatom indices). Environmental indicators (water quality, sediment quality, and physical integrity) also suggested a strong impact of land-use disturbance through urbanization on stream ecosystems. Environmental Integrity Index detected overall stream degradation caused by urbanization in the watersheds.
In conclusion, these studies across geographic regions revealed that landscape indicators incorporating historical land-use offer promise for assessing and predicting biodiversity status in riverine ecosystems impacted by land-use disturbances.
