Ecological and toxicological effects of inorganic nitrogen pollution in aquatic ecosystems: A global assessment.

Although there is growing concern that amphibian populations are declining globally, much of the supporting evidence is either anecdotal or derived from short-term studies at small geographical scales. This raises questions not only about the difficulty of detecting temporal trends in populations which are notoriously variable, but also about the validity of inferring global trends from local or regional studies. Here we use data from 936 populations to assess large-scale temporal and spatial variations in amphibian population trends. On a global scale, our results indicate relatively rapid declines from the late 1950s/early 1960s to the late 1960s, followed by a reduced rate of decline to the present. Amphibian population trends during the 1960s were negative in western Europe (including the United Kingdom) and North America, but only the latter populations showed declines from the 1970s to the late 1990s. These results suggest that while large-scale trends show considerable geographical and temporal variability, amphibian populations are in fact declining--and that this decline has been happening for several decades.

Quantitative evidence for global amphibian population declines

https://www.fs.fed.us/rm/pubs_other/rmrs_2006_cushman_s001.pdf

Effects of habitat loss and fragmentation on amphibians: A review and prospectus

▪ Abstract Declines and losses of amphibian populations are a global problem with complex local causes. These may include ultraviolet radiation, predation, habitat modification, environmental acidity and toxicants, diseases, changes in climate or weather patterns, and interactions among these factors. Understanding the extent of the problem and its nature requires an understanding of how local factors affect the dynamics of local populations. Hypotheses about population behavior must be tested against appropriate null hypotheses. We generated null hypotheses for the behavior of amphibian populations using a model, and we used them to test hypotheses about the behavior of 85 time series taken from the literature. Our results suggest that most amphibian populations should decrease more often than they increase, due to highly variable recruitment and less variable adult mortality. During the period covered by our data (1951–1997), more amphibian populations decreased than our model predicted. However, there ...

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Global Amphibian Declines: A Problem in Applied Ecology

The authors attempted a complete review of the empirical literature on effects of roads and traffic on animal abundance and distribution. They found 79 studies, with results for 131 species and 30 species groups. Overall, the number of documented negative effects of roads on animal abundance outnumbered the number of positive effects by a factor of 5; 114 responses were negative, 22 were positive, and 56 showed no effect. Amphibians and reptiles tended to show negative effects. Birds showed mainly negative or no effects, with a few positive effects for some small birds and for vultures. Small mammals generally showed either positive effects or no effect, mid-sized mammals showed either negative effects or no effect, and large mammals showed predominantly negative effects. The authors synthesized this information, along with information on species attributes, to develop a set of predictions of the conditions that lead to negative or positive effects or no effect of roads on animal abundance. Four species types are predicted to respond negatively to roads: (i) species that are attracted to roads and are unable to avoid individual cars; (ii) species with large movement ranges, low reproductive rates, and low natural densities; and (iii and iv) small animals whose populations are not limited by road-affected predators and either (a) avoid habitat near roads due to traffic disturbance or (b) show no avoidance of roads or traffic disturbance and are unable to avoid oncoming cars. Two species types are predicted to respond positively to roads: (i) species that are attracted to roads for an important resource (e.g., food) and are able to avoid oncoming cars, and (ii) species that do not avoid traffic disturbance but do avoid roads, and whose main predators show negative population-level responses to roads. Other conditions lead to weak or non-existent effects of roads and traffic on animal abundance. The authors identify areas where further research is needed, but they also argue that the evidence for population-level effects of roads and traffic is already strong enough to merit routine consideration of mitigation of these effects in all road construction and maintenance projects.

/pdf/effects-of-roads-on-animal-abundance-an-empirical-review-and-1lbgf8c4mw.pdf

Effects of Roads on Animal Abundance: an Empirical Review and Synthesis

Effects of road de-icing salt (NaCl) on larval wood frogs (Rana sylvatica)

The effects of predatory fish on amphibian species richness and distribution

Increasing nitrate levels in surface and ground waters are of global concern. Effects of nitrates on human health are well documented, but effects on amphibians have received little attention. I exposed Bufo americanus (American toad), Pseudacris triseriata (chorus frog), Rana pipiens (leopard frog), and Rana clamitans (green frog) tadpoles to ammonium nitrate fertilizer in water. In acute tests, mortality varied among species (96-h LC50; 13.6-39.3 mg/L NO3-N) and significant weight loss occurred. In chronic tests (100 d; 0, 2.5, 5, 10 mg/L NO3-N) chorus frog and leopard frog tadpoles had significantly lower survivorship in the 10-mg/L treatments, but green frog survivorship was not affected. Number of chorus frogs metamorphosing was significantly lower in the 10-mg/L treatment, but development time was not affected. In acute exposures, reduced activity, weight loss, and physical abnormalities were observed. Toxic effects of ammonium nitrate occurred in all four species at concentrations that are commonly exceeded in agricultural areas globally. Nitrate fertilizers may play a role in the apparent global amphibian decline.

Acute and chronic toxicity of ammonium nitrate fertilizer to amphibians from southern ontario

Increasing attention is being devoted to the dynamics of interacting local populations of species, especially the role of changes in incidence that affect regional persistence. The status of species in a regional context may be determined more by meta- population dynamics than by purely demographic birth and death processes. The contrast between local and regional views of species' persistence is illustrated today by discussion of the status of amphibians. The amphibian fauna may provide an important indicator of the impact of anthropogenic disturbance to wetland ecosystems. We assessed the status of 11 amphibian species in southwestern Ontario, Canada, by estimating species richness, changes in presence and absence, and incidence at 97 ponds from 1992 to 1994. We detected a significant reduction in amphibian species richness in one of three regions. This loss of diversity relative to the historical species complement is a consequence of the land use history. We observed surprisingly high turnover of species at ponds, with increased inci- dence varying from 0.07 to 0.29 species per pond per year, and decreased incidence ranging from 0.16 to 0.30 species per pond per year. The incidence of common species across years included both declines (leopard frog, Rana pipiens) and increases (American toad, Bufo americanus). For eight relatively rare species, losses exceeded gains between 1992 and 1993, but this pattern was reversed between 1993 and 1994. Understanding environmental factors that determine the status of species will require an expanded, large-scale view of groups of populations (metapopulations) and their spatial dynamics.

Regional Dynamics and the Status of Amphibians

https://www.glel.carleton.ca/PDF/roadPub/08/08EigenbrodetalBiolCons.pdf

Stephen J. Hecnar

Papers

Effects of road de-icing salt (NaCl) on larval wood frogs (Rana sylvatica)

The effects of predatory fish on amphibian species richness and distribution

Acute and chronic toxicity of ammonium nitrate fertilizer to amphibians from southern ontario

Regional Dynamics and the Status of Amphibians

The relative effects of road traffic and forest cover on anuran populations