Issues and approaches in assessing cumulative impacts on waterbird habitat in wetlands

Abstract

/ Wetlands are attractive to vertebrates because of their abundant nutrient resources and habitat diversity. Because they are conspicuous, vertebrates commonly are used as indicators of changes in wetlands produced by environmental impacts. Such impacts take place at the landscape level where extensive areas are lost; at the wetland complex level where some (usually small) units of a closely spaced group of wetlands are drained or modified; or at the level of the individual wetland through modification or fragmentation that impacts its habitat value. Vertebrates utilize habitats differently according to age, sex, geographic location, and season, and habitat evaluations based on isolated observations can be biased. Current wetland evaluation systems incorporate wildlife habitat as a major feature, and the habitat evaluation procedure focuses only on habitat. Several approaches for estimating bird habitat losses are derived from population curves based on natural and experimentally induced population fluctuations. Additional research needs and experimental approaches are identified for addressing cumulative impacts on wildlife habitat values.Wetlands are attractive to many species of wildlife, often because of their great productivity, which provides nutrients and other resources used by diverse groups (Odum 1971, Tiner 1984. In addition, wetlands may be structurally diverse, providing unique habitats to which species have adapted. Certain groups of wildlife, notably birds, are among the most conspicuous of wetland animals, and because they often are tied to specific life forms of vegetation, assessment of habitat involves features such as vegetation structure that are also useful in classification of wetland types and in assessing other wetland values.Concerns over cumulative impacts of human actions on wetland habitats seem to have focused on two major types o~ perturbations: (1) cumulative losses of wetlands from multiple causes, resulting in reduced size, changes in pattern, fragmentation, reduced number, or reduced contiguity between wetlands; or (2) repeated perturbations such as contamination by single or multiple pollutants. In both cases, the effect of the impact is that the individual wetlands, wetland complexes, or wetland districts no longer function as habitat at their former levels--if at all. But there, are many other perturbations that affect wetlands in less conspicuous but significant ways, such as modification of water levels on a landscape or watershed scale, excessive grazing or repeated fires that modify detrital cycleg, increases in siltation that influence the nutrient base or turbidity and hence the nature and rate of plant succession, changes in salinity due to water , for a more complete list related to wildlife habitat issues). Moreover, many of these influences can operate at different levels; partial drainage is more serious in concert with heavy siltation, at the early seed germination and plant growth stages, when bird nesting is at its peak, or when it occurs regularly each...

Developing the scientific basis for assessing cumulative effects of wetland loss and degradation on landscape functions: Status, perspectives, and prospects

“…The life-support function of wetland landscapes is the most vaguely defined, the most variable in space and time, the richest in terms of approaches proposed for assessment, and the most obvious in terms of having tight connections to landscape characteristics (Sather and Stuber 1984, Harris 1988, Weller 1988, and Klopatek 1988. At the same time, it is the most contentious area under debate in the literature (e.g., S imberloff and Abele 1982, Simberloff and Gotelli 1984, Soul~ and Simberloff 1986, Simberloff and Cox 1987cf.…”

A Regional Guidebook for Applying the Hydrogeomorphic Approach to Assessing Wetland Functions of Prairie Potholes

“…Wildlife species diversity is generally highest when the wetland is structurally complex (Weller 1987). No single species, or species guild, can serve as a definitive, all-inclusive indicator of wetland habitat functions or carrying capacity (Weller 1988).…”

Management practices to enhance wildlife diversity of man-made fish ponds: the importance of the hydroperiod

“…At the landscape scale, fish farms are typically clusters of ponds with different-aged fish and varying hydroperiods. Ideally, closely spaced yet differently operated ponds might support various community types and complement each other to yield high beta diversities (Weller, 1988;Wezel et al, 2014). In amphibians, wetland complexes with a range of hydroperiods may facilitate temporal segregation to avoid interspecific competition or predation (cf.…”

“…Amphibians and birds commonly breed within carp ponds (e.g. Hartel et al, 2007;Broyer and Curtet, 2013) and could be used as flagships for wider conservation efforts or as indicators of wetland change (Weller, 1988;Walls et al, 2014; but see Guareschi et al, 2014). We have shown in previous papers that ponds with different-aged (-sized) fish provide habitats of different suitability for wildlife (Kloskowski, 2010;Kloskowski et al, 2010).…”