In parts of Australia, vast areas of native vegetation have been cleared and replaced by our cities, farms, and infrastructure. When native vegetation is removed, the habitat and resources it provides for native wildlife are invariably lost.
Our environmental laws and most conservation efforts tend to focus on what this loss means for species that are in danger of extinction. This emphasis is understandable: the loss of the last individual of a species is deeply saddening and can be ecologically devastating.
But what about the numerous other species also affected by habitat loss, which have not yet become rare enough to be in danger of extinction? These animals and plants, variously described as "common" or "least concern," are being taken away from their habitat. This loss generally escapes us.
These common species have intrinsic ecological value. But they also provide important opportunities for people to connect with nature, experiences that are under threat.
The “loss rate”: tracking destruction
We developed a measure called the loss rate to communicate how habitat loss affects multiple species of Australian birds. Our measurement showed that in Victoria, and in South Australia and New South Wales, more than 60% of 262 native birds have lost more than half of their original natural habitat. The vast majority of these species are not formally recognized as threatened with extinction.
It's a similar story in the Brigalow Belt of central New South Wales and Queensland. The picture is brightest in the northern savannas in the upper part of Australia, where large tracts of native vegetation remain, despite widespread threats such as inappropriate fire regimes.
We also found that in some areas, such as southeast Queensland and the humid tropical region of North Queensland, the removal of a single hectare of forest habitat can affect up to 180 different species. In other words, small amounts of loss can affect a large number of (mostly common) species.
Our index allowed us to compare how different groups of birds are affected by habitat loss. Australia's parrots have been hit hard by habitat loss, because many of these birds are found in the places where we live and grow our food. Birds of prey such as eagles and owls, as a group, have been less affected. This is because many of these birds are found widely in the less developed arid interior of Australia.
Loss of habitat means far fewer birds:
Our study shows that many species have lost a lot of habitat in certain parts of Australia. We know that habitat loss is one of the main drivers of population decline and free fall of animals globally. One measure of vertebrate population trends, the Living Planet Index, reveals that the populations of more than 4,000 species of vertebrates around the world are, on average, less than half what they were in 1970.
In Australia, the trend is no different. Populations of our threatened birds declined by an average of 52% between 1985 and 2015. Alarmingly, the populations of many common Australian birds are also declining, and habitat loss is a major cause. Along the heavily populated east coast of Australia, declines in the population of many common species have been observed, including the rainbow bee-eater, the double-barred finch and the pale-headed rosella.
This is a major problem for the health of the ecosystem. Common species tend to be more numerous and therefore play many roles that we depend on. Our parrots, pigeons, melons, robins and many others help pollinate flowers, spread seeds and control pest insects. In both Europe and Australia, declines in common species have been linked to a reduction in the provision of these vital ecosystem services.
Common species are also the ones we associate most with. Because they are more abundant and familiar, these animals provide important opportunities for people to connect with nature. Think of the simple pleasure of seeing a colorful robin perched atop a rural fence post, or a vibrant parrot running over the treetops of a suburban stream. The decline in common species can contribute to diminishing opportunities for us to interact with nature, leading to an "extinction of the experience", with associated negative implications for our health and well-being.
We must not wait until its too late
Our study aims to highlight common species. They are of crucial importance, yet their habitat erosion receives little attention. Keeping them now is sensible. Waiting until they have decreased before we act will be costly.
These species need more formal recognition and protection in conservation and environmental regulation. For example, greater attention should be paid to common species and the role they play in ecosystem health in assessing new infrastructure developments under Australia's federal environmental laws (formally known as the Environmental Protection Act and Conservation of Biodiversity 1999).
We should be acting now to conserve common species before they fall into danger. Without dedicated attention, we run the risk of these species declining before our eyes, without our realizing it.