EDGE species are threatened by a number of different factors in today’s rapidly changing world. Often these factors interact in a complex and unpredictable way. Research is crucial to find out more about these threats, and provide sound information on which to base conservation programmes.
Follow the links to find out more about threats particularly affecting amphibians.
Human alternation of habitat is the single biggest threat to plant and animal species. Human pressure on global ecosystems is intensifying as global populations rise, settlements expand, and natural resource extraction accelerates. Furthermore, habitat degradation and fragmentation reduces the quality of what remains. It is now estimated that humans have altered between one third and one half of the Earth’s land surface. Factors such as forestry and agriculture have major effects on endangered species populations. Roads, fields and urban areas represent significant barriers to movement, and may also result in unnaturally high population densities for the available food supplies. Of longer-term importance is the probability of inbreeding and loss of genetic variation in small isolated populations. Combined, these factors make populations extremely vulnerable to other threats such as disease and environmental catastrophes.
The damming of rivers and the reduction in the quality of water bodies can be extremely detrimental to the survival of many water-dependent species, such as river dolphins and amphibians. Mining is also a major threat, polluting water and resulting in massive mechanical destruction of many EDGE species and their habitat.
Introduced and invasive species
Humans have spread a great many non-native animals and plants around the world and they have done so at an unprecedented rate in the last century. The establishment and spread of non-native or “exotic” species are a major threat to worldwide biodiversity, and many species have been greatly impacted by introduced species through direct predation, competition and the introduction of diseases. Communities of species develop over a long period of time, and survive in delicately balanced ecosystems. The movement of species between separate ecosystems can cause great upset, especially if an exotic species rapidly reproduces, establishes itself competitively within the new system and becomes “invasive”. The cane toad (Bufo marinus), introduced to Australia in 1935 as a means of pest control, has had a negative effect on native amphibian populations, while the spread of black and brown rats around the globe has led to the extinction of many island species over the past 500 years.
Many animal species are highly attractive or charismatic, and have become popular among collectors in the pet trade. Generally, the rarer the species the higher the demand and, therefore, the rarer the species becomes. Animals caught in the wild are often kept in crowded cages awaiting final shipment to their destination. The ones that do get there alive often only survive for a short time in captivity before being unceremoniously replaced. Furthermore, some species are over hunted for food, or harvested for their various properties, such as skin toxins, which have numerous ceremonial and hunting-related uses, or horns, for use in traditional medicine.
A number of different pollutants negatively impact animal species, particularly those inhabiting aquatic environments. Rivers and streams are frequently polluted by a wide range of agricultural, industrial and other wastes, many of which have not been properly treated. These pollutants can lead to a decrease in oxygen levels in the water, a feature often associated with dense algal blooms. Many species die as a result of suffocation or starvation as their food supplies are rapidly destroyed by the algae. Non-lethal effects of pollutants include, reducing reproductive success, weakening immunity and indirectly reducing food and/or habitat availability.
Global climate change is a huge issue facing life on Earth. The consensus opinion is that human activities have caused stable climatic systems to change unpredictably. Temperatures and rainfall patterns are changing, resulting in global warming and an increased frequency of climatic disasters or “extreme weather”, such as hurricanes and tornados, droughts and floods. All life on earth is likely to be affected, but some groups appear to be more vulnerable that others. Find out more about the effects of climate change and UV radiation on amphibians here.
Disease can be a major threat to all species, particularly if populations have already experienced declines as a result of other factors. Virulent diseases caused by viruses, fungi and bacteria are a particular threat to amphibians, killing thousands, if not millions, of animals each year. Find out more about how disease is emerging as one of the major threats to amphibian species worldwide here.