A model-based assessment of anthropogenic disturbance on lotic macroinvertebrate assemblages

Traditionally, the effects of anthropogenic disturbance on biological assemblages are elucidated by comparing an assemblage observed at a site to one that represents a minimally disturbed state. Unfortunately, defining a minimally disturbed state is extremely challenging because of the extent of human disturbance. We use a national scale dataset and a two-stage modeling approach to assess how benthic macroinvertebrate assemblages at 1,824 sites would change if common anthropogenic disturbances were removed from in-stream physiochemical variables. First, we used random forest models and current landscape data to predict physiochemical conditions and then infer abiotic condition in the absence of disturbance. Second, we combined these estimates with joint species distribution models to predict the assemblage that would occur in these undisturbed conditions. Random forest models explained 48 – 75% of the variation in total nitrogen, phosphorous, sulfate, chloride, and substrate diameter. Generally, nutrient and salinity concentrations were higher, and substrates were finer than predicted to be without disturbances. Using this physiochemical data joint species distribution models accurately explained genus richness (R2 = 0.73 – 0.85) and composition (Jaccard similarity index = 0.48 – 0.55). Depending on the ecoregion, we found that genus richness could change at 26 – 61% of sites if disturbance was removed. Different responses were observed for insect and non-insect taxa. For example, under anthropogenic disturbance, occurrence probabilities for Ephemeroptera, Plecoptera and Trichoptera tended to decrease at 5 – 26% of sites while occurrence probabilities for Mollusca and other non-insect, non-arthropod taxa increased at 5 – 33% and 11 – 24% of sites, respectively. Importantly, our framework provides an avenue for evaluating the effects of anthropogenic disturbance on macroinvertebrate assemblages without relying on defining reference sites. 

Impact/Purpose

This journal article titled,  "A model-based assessment of anthropogenic disturbance on lotic macroinvertebrate assemblages of the contiguous United States", evaluates the potential effects of human disturbance on benthic macroinvertebrate assemblages using a two-stage modeling approach. Traditionally, the effects of anthropogenic disturbance on biological assemblages are elucidated by comparing an assemblage observed at a site to one that represents a minimally disturbed state. Unfortunately, defining a minimally disturbed state is extremely challenging because of the extent of human disturbance. The concept of least-disturbed is often used to identify sites that are the best remaining given today's landscape but is difficult to quantify, can be spatially biased, and potentially vary from one region to another. We leveraged physical habitat and benthic macroinvertebrate assemblage data collected by the National Rivers and Stream Assessment to investigate the potential effects of human disturbance on benthic assemblages without the need to identify reference sites. Beyond illustrating how human disturbance may have changed biological assemblages from a historical state, our framework may be expanded to include future scenarios and evaluate how biological assemblages might respond to restoration efforts or future changes in physiochemical conditions. 

Citation

Kopp, D., J. Stoddard, Phil Kaufmann, A. Herlihy, R. Hill, M. Brehob, AND R. Sabo. A model-based assessment of anthropogenic disturbance on lotic macroinvertebrate assemblages. ESA Journals, 16(10):e70361, (2025). [DOI: 10.1002/ecs2.70361]

DOI: A model-based assessment of anthropogenic disturbance on lotic macroinvertebrate assemblages