Habitat Destruction

There are over six billion humans on the planet, but not nearly enough natural resources to support us in a sustainable manner at our current rate of consumption. It is not surprising then that habitat loss is one of the most significant threats to amphibian populations. Humans alter and destroy habitat by logging forests, draining swamps, covering streams with housing developments and malls, damming rivers and draining them for irrigation, introducing weeds and livestock, and a variety of other actions that negatively affect amphibians.

Deforestation in developing countries

The bulk of deforestation is concentrated in tropical regions, where amphibian biodiversity is greatest. Each year, nearly 6 million hectares (15 million acres) of the world's tropical forests are logged. Deforestation in tropical countries is extremely difficult to halt, as the subsequent development of agriculture and infrastructure is seen as the first crucial step toward economic development. In South America, deforestation has severely degraded the ecosystem integrity in the Amazon Basin, the Atlantic forests of Brazil and the coastal plains of Ecuador and Peru. The Amazon contains over half of the world’s remaining tropical forest but its size is rapidly diminishing: approximately 2 million hectares are cleared each year in the Brazilian Amazon alone. Slash and burn agriculture threatens amphibian biodiversity throughout Indonesia, Malaysia and sub-Saharan Africa.

Deforestation in western countries

Deforestation is by no means restricted to developing countries: the picture at right was taken immediately adjacent to Australia's Conondale National Park, former home of the now extinct Southern Gastric-Brooding Frogs Rheobatrachus silus and Southern Day Frogs Taudactylus diurnus. In Australia, habitat destruction is associated with declines in 18 of the 40 threatened frog species, and is the primary cause of population declines in lowland frogs. Populations of Houston toads Bufo houstonensis in Texas have been drastically reduced by deforestation, and there are now only about 3,000 individuals remaining. (Photo and graffiti by K. Kriger)

Death by a thousand cuts

Although some amphibian species decline rapidly when the forest cover is removed, most species suffer a gradual depletion of populations, and the overall impacts are not realized until the species has disappeared from a significant part of its former geographic range. This gradual depletion of suitable habitat through the accumulation of small-scale habitat loss (urban and rural expansion) has been described as “death by a thousand cuts”. Whereby no single development (i.e. housing complex, shopping center) is responsible, the accumulation of many small developments eventually leads to the complete loss of the original habitat for the species. Loss of local populations results in a decrease of genetic diversity, and thus a reduction in the evolutionary potential for species to adapt to environmental changes such as global warming, pesticide contamination or introduced infectious diseases.

Loss of ephemeral wetlands

Habitat Destruction Ephemeral wetlands completely dry up for a portion of each year, and thus are perfect for amphibians since they do not harbor predatory fish. These wetlands tend to contain unique amphibian assemblages, yet often receive little legal protection. The photo on the right is of an ephemeral pond that is about 10cm (4 in) deep and only holds water for a couple months of the year. This pond supports large populations of American toads Bufo americanus, Gray Treefrogs Hyla versicolor and Spring Peepers Pseudacris crucifer. Creating legislature to protect ephemeral wetlands is a top priority for amphibian conservation.

Secondary effects of habitat destruction

The land use change that occurs after a natural habitat is destroyed may lead to an increased chance of direct predation by domestic animals, and may facilitate the emergence of infectious diseases.

Protecting habitat for all amphibian life stages

Though the conservation of amphibians has traditionally focused on protecting breeding habitats (i.e. ponds & streams), the habitats used by all amphibian life history stages (eggs, tadpoles, juvenile & adult stages) must be protected. Many amphibians utilize both the water bodies and the terrestrial areas several kilometers from the breeding sites. Further, roads and developments often divide an amphibian's required habitats, making breeding migrations from the forest to the wetlands either dangerous or impossible.

Learn about other threats to frogs

Chytridiomycosis & other infectious diseases
Pollution & Pesticides
Climate Change
Invasive Species
Over-Harvesting

Deforestation