The southern brown tree frog can climb concrete walls to reach urban ponds.
Credit: Wikipedia
The salmon's annual swim up the mighty river systems of the world is no mean feat. After a few years in the open ocean, a salmon reaches sexual maturity and decides to return its natal breeding ground. During the risky and arduous journey, a salmon would fight its way upstream - sometimes for thousands of kilometres.
That was, of course, until humans came along and constructed massive dams in their path. Then it only got tougher. The Columbia River, on the west coast of North America, now consists of a series of reservoirs, for example. While they no doubt disrupted riverine environments and the lives of migrating fish within, the salmon population fought back, launching a rapid response to human obstacles.
Studying Pacific salmon in the Columbia River system, Robin Waples and colleagues at the Northwest Fisheries Science Centre in Seattle, Washington, found that juveniles faced with a dam-ridden path wait longer to venture out to sea, growing larger to better deal with the more demanding journey, as they reported in a 2007 paper in Molecular Ecology.
Human modification to the landscape has prompted significant change in salmon populations over a short amount of time. Whether the change is an evolutionary or a plastic response remains an open - but critical - question, say the researchers.
Salmon could be facing a 'Darwinian debt': after several generations, the population of salmon have adapted to these human-imposed conditions, and this could be reflected in their gene pool. So if all the dams were suddenly removed and the Columbia River returned to its once mighty, free-flowing state, this could pose a problem to salmon - they may no longer be suited to such conditions.
What is happening to salmon is happening to animals in ecosystems all over the world. Few, if any, places have escaped the reaches of human modification. But nowhere is this more apparent than in cities. Questions of who survives despite anthropogenic change - and how - are fuelling the growing field of urban ecology. "It's interesting to know what allows species to persist in cities," says Barry Brook, environmental scientist at the University of Adelaide. "It's a new sort of ecology."
Over half of the world's population now lives in urban environments, according to the UN, and concrete jungles around the world keep expanding. "Cities are going to be where animals are going to be forced to live," says urban ecologist Chris Daniels of the University of South Australia. With the disappearance of untouched natural spaces and biodiversity, understanding ecosystem dynamics in cities becomes crucial.
Suddenly, animals are dealing with challenges they'd never have encountered in the untrammelled wilderness and this human-built environment is acting as a catalyst for rapid adaptations. Adaptations are being recorded in various animals' feeding habits, communications or migratory patterns - and this is likely resulting in genetic changes at much higher rates than occur naturally.
Cartoon idea based on this story:
I'm sure that if Cosmos were a daily newspaper, one of the staff cartoonist would have submitted the following:
An environmental group approaches a demolition crew about to destroy a condemned high-rise community, protesting that the old buildings are the natural habitat of some rare animal that has adapted to urban life.
Cartoon
Good one !!