Low forest-loss thresholds threaten Amazonian fish and macroinvertebrate assemblage integrity

Biological assessment of western USA sandy bottom rivers based on modeling historical and current fish and macroinvertebrate data

“…A similar perspective is offered when applying Threshold Indicator Taxa Analysis to assessments of pristine tropical forests being transformed by forest removal. For example, sensitive fish species disappeared at 1 and 6% of forest‐loss at catchment and riparian spatial extents, respectively (R. T. Martins et al, 2021). Sensitive macroinvertebrates were lost at 1 and 11% of forest loss at catchment and riparian spatial extents, respectively (Brito et al, 2020; R. T. Martins et al, 2021).…”

“…For example, sensitive fish species disappeared at 1 and 6% of forest‐loss at catchment and riparian spatial extents, respectively (R. T. Martins et al, 2021). Sensitive macroinvertebrates were lost at 1 and 11% of forest loss at catchment and riparian spatial extents, respectively (Brito et al, 2020; R. T. Martins et al, 2021). Thus, more commonly implemented biological assessments that are based on current least‐disturbed reference sites are biased towards indicating better ecological status than those based on historical perspectives, because in many cases sensitive‐rare and ubiquitous species have already been extirpated from the entire region being assessed (Davies & Jackson, 2006; Leitão et al, 2016).…”

“…Likewise, the original riparian vegetation has been markedly modified (Finch, Wolters, Yong, & Mund, 1995), which would be expected to fundamentally alter the river physical habitat structure and allochthonous inputs that serve as important sources of food and cover for macroinvertebrates (Gregory, Swanson, McKee, & Cummins, 1991). Again, sensitive macroinvertebrates were lost at 11% of riparian forest loss (Brito et al, 2020; R. T. Martins et al, 2021). Although the altered riparian vegetation presumably affected both fish and macroinvertebrate assemblages, the altered flow regime and channel fragmentation by dams likely affected fish migration and recruitment more than macroinvertebrate movements.…”

“…Briefly, this is accomplished by using the residuals from regression lines as the response variables; however, such indices only assess the observed occurrences of non‐rare taxa versus their expected occurrences. Rare, often sensitive, taxa are omitted from such analyses and those taxa are often the first to disappear during the early stages of anthropogenic disturbances (Davies & Jackson, 2006; Leitão et al, 2016; R. T. Martins et al, 2021). Also, some tolerant taxa are more likely to occur in the early stages of anthropogenic disturbance, thereby, resulting in no change or even an increase in taxa richness (Davies & Jackson, 2006; R. T. Martins et al, 2021).…”

“…Rare, often sensitive, taxa are omitted from such analyses and those taxa are often the first to disappear during the early stages of anthropogenic disturbances (Davies & Jackson, 2006; Leitão et al, 2016; R. T. Martins et al, 2021). Also, some tolerant taxa are more likely to occur in the early stages of anthropogenic disturbance, thereby, resulting in no change or even an increase in taxa richness (Davies & Jackson, 2006; R. T. Martins et al, 2021). Partly because of the shortcomings of species richness indicators, Karr (1981) proposed using multimetric indices (MMIs).…”