Changes in species richness and composition of boreal waterbird communities: a comparison between two time periods 25 years apart

Abstract

Global measures of biodiversity indicate consistent decline, but trends reported for local communities are more varied. Therefore, we need better understanding of mechanisms that drive changes in diversity of local communities and of differences in temporal trends between components of local diversity, such as species richness and species turnover rate. Freshwater ecosystems are vulnerable to multiple stressors, and severe impacts on their biodiversity have been documented. We studied species richness and composition of local boreal waterbird communities in 1990/1991 and 2016 at 58 lakes distributed over six regions in Finland and Sweden. The study lakes represented not only local trophic gradients but also a latitudinal gradient in the boreal biome. While species richness tended to be lower in 2016 than in 1990/1991, species turnover was relatively high. Within foraging guilds, local species richness of diving ducks and surface feeding waterbirds decreased, whereas that of large herbivores increased. The number of species gained in local communities was higher in lakes with rich vegetation than in lakes with sparse vegetation. Conservation of boreal freshwater ecosystems would benefit from recognizing that large-scale environmental changes can affect local diversity via processes operating at finer scales.

Population change in breeding boreal waterbirds in a 25‐year perspective: What characterises winners and losers?

“…Decrease and loss of species as described above are often associated with dramatic shifts in abundance and turnover of other species locally (Dornelas et al, 2014;Magurran et al, 2015;Pöysä et al, 2019). However, there is rarely time or resources to study each species in isolation in order to understand such patterns and the causal processes behind them.…”

“…The timing of surveys was adjusted to account for differences in spring phenology among regions, mainly based on wetland ice-out dates and vegetation development (e.g. In 2016, we repeated surveys at the same lakes using the same methods and field protocol as in 1990/1991, with one exception; lakes in region 1 (Lappi, see 1) were visited only once in 2016, and the date of this single count was between the dates of the two counts in 1991 (see Table S4 in Pöysä et al, 2019). In 2016, we repeated surveys at the same lakes using the same methods and field protocol as in 1990/1991, with one exception; lakes in region 1 (Lappi, see 1) were visited only once in 2016, and the date of this single count was between the dates of the two counts in 1991 (see Table S4 in Pöysä et al, 2019).…”

“…In 2016, we repeated surveys at the same lakes using the same methods and field protocol as in 1990/1991, with one exception; lakes in region 1 (Lappi, see 1) were visited only once in 2016, and the date of this single count was between the dates of the two counts in 1991 (see Table S4 in Pöysä et al, 2019). For more information about the representativeness of the data, see Supplementary Material in Pöysä et al (2019). Hence, the final sample for the present analysis comprised data from 58 lakes.…”

“…This habitat index is relevant to use for the purpose of the present study, as there is a robust correlation between lake-level species richness of waterbirds and lake-specific habitat index in this data set, for 1990/1991 as well as for 2016 (Figure S1inPöysä et al, 2019). We then used principal component analysis (PCA) to derive a single gradient of habitat structure, along which the lakes were ordered.…”

Relationships between breeding waterbird abundance, diversity, and clear water status after the restoration of two shallow nutrient‐rich Danish lakes

“…Alarming trends of decline in breeding waterbird populations exploiting eutrophic boreal wetlands (Lehikoinen et al, ; Lehikoinen, Lehikoinen, Mikkola‐Roos, & Jaatinen, ), as well as more recent declines in oligotrophic wetlands (Pöysä et al, ), underline the need for more information on how local site conditions contribute to large‐scale processes affecting waterbird population dynamics. In this context, the results provide support for the argument that eutrophication (from anthropogenic sources such as wastewater, industrial pollution, and agricultural run‐off????????)…”