Wildlife and landscape science research topics: contaminants and wildlife

Article Title

Contaminants and Wildlife

Northern leopard frog gonad with both male and female tissue | Photo: C. Mackenzie, Trent University
Various natural and anthropogenic chemicals and compounds can pose a risk to wildlife. Each contaminant has different characteristics and can affect wildlife in different ways. Understanding these different properties, pathways and effects, alone and in combination, is necessary to understand the impacts of contaminants on wildlife and ecosystem health.

The science produced by wildlife and landscape researchers has been used in many programs and policies to help inform decision making and conservation efforts to protect Canadian species and ecosystems against harmful legacy substances.

Ongoing research is continually identifying new chemicals of concern and ensuring that robust science informs decisions about new and emerging contaminants.

Endocrine Disruptors

Deformed green frog Rana clamitans from a Quebec farm pond | Photo: M.Ouellet, McGill University
Endocrine disruptors are substances that mimic hormones and can interfere with the body’s normal physiological and metabolic processes that regulate growth, development, tissue function, reproduction and behaviour.

These substances have different life spans and consist of drugs, pesticides, industrial chemicals, metals and natural compounds often found in municipal, textile, mining and pulp and paper effluents.

Some examples are:

Increased exposure can reduce an organism’s ability to respond adequately to stressful situations, disrupt hormone flow, alter sexual characteristics, reduce birth rate, cause birth defects and impair development.

These factors may affect wildlife at the individual, population and community levels, thereby impacting the structure of biological communities and possibly reducing biodiversity.

Current research on endocrine disruptors focuses on:

  • Understanding and investigating the ecotoxicology of contaminant and metabolite exposure on species and ecosystems
  • Investigating the sub-organismal effects of contaminant exposure
  • Conducting assessments of species and overall ecosystem health
  • Investigating the effects of endocrine disrupting compounds and metabolites on the reproductive, immune and other systems of various wildlife species including polar bears, marine mammals, mink, amphibians, snapping turtles, bald eagle, peregrine falcon, herring gulls, and many other avian species
  • Conducting multi-generational laboratory investigations of the subtle effects of exposure to chemicals at early life stages, using model species such as the zebra finch
  • Examining the fate and pathways of endocrine disruptors in marine and aquatic food webs
  • Examining soil and water interactions to better understand the pathways of transport for nutrients and contaminants
  • Studying the chemical composition in suspected sources of endocrine disruption including industrial effluents and land use-agriculture practices
  • Species specific, contaminant-mediated enzyme induction and associated mechanistic pathways of contaminant metabolism/biotransformation leading to endocrine-disrupting products in wildlife
  • An in vitro competitive binding assays using e.g., recombinant thyroid hormone transport proteins from a bird and mammalian models to understand the structure-activity relationships and relative potencies of chlorinated, brominated or fluorinated compounds, and especially phenolic metabolites and complex mixtures from wildlife, to influence e.g., circulating thyroid hormone status

Pesticides and Herbicides

The emphasis of pesticide research is on predicting and documenting the impacts of pesticide use on wildlife, and proposing strategies to mitigate these effects.

Photo of herbicide application by a tractor pulling a large spray boom. Herbicide drift can be observed | Photo: Céline Boutin

Exposure and potential effects on health can occur when wildlife enter fields treated with pesticides. Also, it is generally accepted that some non-target sites and organisms may be affected through drift, volatilization, runoff, leaching, or displacement of soil particles through wind erosion.

This can affect wildlife in the vicinity of application and can have repercussions at various trophic levels in the affected area.

Current research on pesticides and herbicides focuses on:

  • Herbicide bleaching on species of fern | Photo: Céline Boutin
    Field research and modeling of acutely toxic insecticides in both liquid and granular form to assess their probability of causing bird kills
  • Conducting laboratory experiments to define toxicity thresholds and to develop new assays, such as the effects of rodenticides on blood clotting in birds, which can be applied to assess toxicity in the field
  • Standardizing methods to rear and test toxicity in amphibians including the examination of diet, holding densities and proper environmental conditions for rearing, breeding and hibernation
  • Improving the methodology of testing herbicide toxicity on plants, with a special focus on native species in order to make regulatory testing more representative of species found in habitats to be protected
  • Assessing the importance of non-dietary pesticide exposure routes in birds
  • Developing tools and software to measure the total environmental footprint of different pesticide products
  • Comparing pollinator diversity and bird nesting success in different agricultural regimes
  • Verification of existing pesticide regulatory programs, ensuring that they are scientifically robust to protect native species and habitats
  • Development of new tools and approaches to model species loss due to pesticide use, and incorporating these factors into ecological risk assessment science

Persistent Organic Pollutants (POPs)

Persistent Organic Pollutants (POPs) are chemically stable toxic substances emitted into the environment that are resistant to photolytic, chemical and biological degradation.

Image of herring gull in Great Lakes | Photo: Ian Parsons, Environment Canada
Some examples are:

POPs bioaccumulate mainly in the fatty tissue of living organisms and produce a number of harmful effects in wildlife including reproductive dysfunction, eggshell thinning, metabolic changes, birth defects, cancer, immune system suppression and endocrine disruption.

These effects, alone or in combination, can leave individuals and populations vulnerable to diseases and predation, and can be a contributing factor in population declines.

In the 1970s, Great Lakes monitoring programs alerted scientists to the fact that the eggs of fish-eating birds were becoming so thin that they would crack during incubation. This was a result of DDT exposure, and once banned, levels declined by 10 times and the health of local birds improved.

Researchers have determined that since regulatory actions have been taken against legacy POPs, levels in general have declined by about half, and in some indicator species, such as the herring gull, drastic reductions have occurred.

Considerable work in this field has centered on northern and Arctic regions, where atmospheric processes deposit POPs originating from southern sources.

Breath sampling a polar bear | Photo: Environment Canada

Working in the Arctic with local communities, researchers examine contaminant levels and effects, and work to reduce the risk posed to wildlife and northern communities.

Research on POPs focuses on:

  • Determining the sources, occurrence and dynamics of POPs and their effects on the reproduction, survival, and health of wildlife species, including  Northern environments where POPs have been deposited from long-range atmospheric transport
  • Contributing to national and international working groups and programs to advise Arctic governments and communities on matters relating to wildlife, contaminants and associated issues. These groups include the Arctic Monitoring and Assessment Programme and the Northern Contaminants Program at Indian and North Affairs Canada
  • Focusing on the occurrence of POPs within high trophic level species including seabirds on all of Canada’s coastlines, polar bears and ringed seals in the Arctic, birds and reptiles in the Great Lakes, and soprey and loons in alpine lakes
  • Studying the spatial and temporal patterns and the bioaccumulation and trophodynamics of POPs to better understand and predict POP movements
  • Participating in international cooperative agreements to reduce the international usage of POPs
  • Investigating ‘hot spots’ in the Great Lakes, and elsewhere

Emerging Compounds

While levels of persistent organic pollutants (POPs) have decreased since the 1970s, levels of emerging contaminants have increased and pose growing concern for research communities and the public.

Emerging contaminants are increasing in concentration, occur more widely than predicted and in some cases have unique toxicological properties.

Brominated flame retardants (BFRs), chemicals used as fire suppressants, are one example and are found in common items like textiles, plastics and electrical appliances.

Polybrominated diphenyl ethers (PBDEs) have been of particular concern after studies in the 1990s revealed that these chemicals were found in human milk, but are still at generally low levels. Research on PBDEs, other BFRs and other emerging compounds continues to provide information used in the regulation of chemicals under the Canadian Environmental Protection Act, 1999.

Research focuses on the following areas:

  • American kestrel incubating eggs in nest box |  Photo: Glenn Barrett
    Effects of new and emerging chemicals, especially BFRs, on the reproduction, growth, behaviour and endocrine function of free-ranging and captive birds, including raptors and passerines
  • Develop methods for contaminant trend monitoring
  • Development of biomarkers/bioassays to measure the cumulative effects of emerging substances (pharmaceuticals and nanotoxicology)
  • Studying the bioaccumulation, fate and trophodynamics of emerging contaminants and metabolites in wildlife, food webs and ecosystems
  • Identifying spatial and temporal trends in bioaccumulation on top predators, including gulls, raptors and reptile species
  • Investigating the impacts of exposure to new and emerging chemicals, including BFRs, and other compounds found in municipal effluent on birds and reptiles
  • Analysis of ultra trace levels of contaminants to identify levels of PBDEs in the environment, helping to establish and document the occurrence and patterns of the contaminant pathway
  • Investigating food web dynamics in the Great Lakes and temporal and spatial dietary changes in Great Lakes gulls to accurately assess how contaminant levels are changing in the ecosystem

Further reading

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