Reduction of avian diversity in created versus natural and restored wetlands

Abstract

Natural wetland ecosystems continue to suffer widespread destruction and degradation. Many recent studies argue that artificial or restored wetlands compensate for wetland loss and are valuable for waterbird conservation. However, detailed comparisons of the value of natural, artificial and restored wetlands are lacking. Our aim was to assess if the restoration or creation of wetlands can fully compensate for the loss of natural wetlands for waterbirds. We compared the waterbird communities in a set of 20 natural, restored and artificial wetlands, all of which are considered important for waterbirds and are located within the same protected area (Doñana Natural Space, south‐west Spain). We used different measures of diversity, including phylogenetic relatedness, and the proportion of threatened species at national, European and international levels. We found that artificial wetlands have consistently lower value than restored and natural wetlands, with little difference between the latter two. Natural wetlands are essential for conserving diversity across the tree of life and for threatened species, but restored wetlands can be of similar value and can assure maintenance of key ecological processes. Thus, when economic costs per unit area are similar, resources for wetland conservation are better invested in restoration projects than in wetland creation, and caution is required when suggesting that artificial wetlands compensate for the loss of natural wetlands.

Effect of Protection Level in the Hydroperiod of Water Bodies on Doñana’s Aeolian Sands

“…We checked the 20 irrigation ponds identified in the random sample (Table 2) in historical aerial photos and no one was visible in 1984 (one was a natural pond at that time) while 13 years later, in 1997, 17 of the irrigation ponds (85%) had already been built. Artificial ponds are no substitute for natural temporary ponds, but provide alternative habitats for certain aquatic organisms and can act, in certain situations, as complementary habitats of conservation value [56]; but, in general, artificial water bodies have a reduced biodiversity value [57].…”

Long-Term Monitoring of the Flooding Regime and Hydroperiod of Doñana Marshes with Landsat Time Series (1974–2014)

“…For instance, the 2007-2008 flooding cycle was close to the historical average rainfall (550 mm), but it was unevenly distributed along the cycle. This situation led to an average low hydroperiod in the marsh (mostly red in Figure 7b), which led to a low waterbird diversity [70] and productivity [71] in that year. Not only are natural drivers clearly evidenced in Doñana flooding regime, but anthropic management actions are locally conspicuous.…”

A functional perspective for breeding and wintering waterbird communities: temporal trends in species and trait diversity

“…the so‐called functional structure of a community, is another important aspect of biodiversity that has gained attention during recent years (McGill et al , Naeem et al ). Analyses of functional trait diversity may highlight patterns across ecosystems that are not apparent in taxonomic analyses (Boersma et al ), as they better account for ecological differences among species. For example, changes in the distribution of species in the functional trait space may reveal the loss or gain of extreme trait values, the concentration of species abundances towards the extremes or the center of the occupied trait space, and the packing of individuals in the occupied space.…”

“…Changes in beta diversity may indicate increases in homogeneity or heterogeneity of species and traits among communities. Evaluating changes at both these levels of functional diversity gives insight into the environmental scale driving species and functional trait distributions (Mendez et al , Socolar et al ). Moreover, investigating if trait distributions are dependent on species richness may reveal whether stochastic or deterministic ecological processes are acting on communities (Mouillot et al ).…”

“…They can be monitored with a unique degree of accuracy, in which all individuals can often be counted in wetland ecosystems with a clear boundary. Furthermore, they provide various ecological functions in wetlands including control of populations at lower trophic levels, propagule dispersal and the resulting connectivity between different wetlands, ecosystem engineering and scavenging (Green and Elmberg , Green et al ). At the same time, waterbirds are affected by high rates of wetland loss and degradation (Davidson ) that have caused population declines of many species (Wetlands International ).…”