The black swans in Melbourne's Albert Park are losing their fear of humans, as are local magpies and possums.

Native water dragons in Brisbane are growing longer legs and narrower heads, while squirrel gliders there are inbreeding more.

Even human DNA is subtly changing.

It's all part of a dramatic burst of evolution happening to animals living in or near cities - and scientists think it's being driven in part by air pollution.

In some cases, it's reducing the genetic diversity of species, putting them at risk. But other animals are using this burst of mutation to evolve to better suit city life, making scientists hopeful this new "urban evolution" could end up saving rare and endangered species.

"Human activity is often causing faster evolution," says Professor Marc Johnson from the University of Toronto, a co-author of a new review into the phenomenon published in the journal Science on Friday.

"Whether it is good or bad depends on your perspective."

Evolution occurs when random DNA mutations lead to new, useful adaptations - for example, a more useful beak.

Animals whose adaptations allow them to better exploit their environment have a better chance of breeding and passing on their DNA.

That, in a nutshell, is natural selection.

Air pollution increases the speed at which animal DNA mutates, Professor Johnson says. That is allowing some animals to rapidly evolve to meet the demands of city life.

One of the first studied examples of urban evolution occurred in a species of British moth.

In the 19th and 20th centuries industrial pollution coated the normally light-coloured trunks of trees in the area with thick soot.

Researchers out looking for the peppered moth, which was white with dark speckles, discovered it had evolved dark brown wings which allowed it to hide on soot-stained tree trunks.

More recently researchers have discovered a certain species of fish that has evolved a tolerance to lethal industrial chemicals such as polychlorinated biphenyl, allowing them to live in polluted city waterways.

And in Puerto Rico, crested anoles - a species of lizard - have evolved longer limbs and larger scales on their feet, letting them run through the artificial surfaces of cities faster.

Professor Johnson said evolution was allowing some endangered species to adapt to city life, potentially saving them from extinction.

"But on the other hand, when rats, bed bugs or disease-carrying mosquitoes evolve resistance to pesticides sprayed in cities, most people would consider this a bad thing," he said.

"This is just the way the new human-dominated world works."

In addition to evolving to meet the challenges of city life, animals have also evolved in response to human behaviour.

In Tucson, Arizona, house finches have evolved longer, wider and stronger beaks.

Researchers discovered they had started feeding off sunflower seeds at birdfeeders, which are larger and have a thicker shell than the seeds they normally eat.

A long, strong beak means the finches had access to more of the seeds - a strong evolutionary advantage.

Some urban species, such as Victoria's black swans, are starting to lose genes that are associated with harm avoidance and wariness towards humans.

This benefits the birds by letting them feed on human rubbish and quickly go after any crumbs a passerby might drop on the ground.

Our cities are even pushing human DNA to evolve.

In cities with longer histories of human settlement, local populations have higher proportions of genes that give resistance to old world plagues such as tuberculosis or leprosy.

University of South Australia professor of biology Chris Daniels believes we should embrace urban evolution and start building cities that allow animals to coexist with humans.

"What urban evolution does is give hope for a lot of species," he said.

"We should put real work into thinking of a city not just as a desert for wildlife, but one that we can adjust a bit to be home to lots of species

"Those species will evolve and adapt to various degrees to our cities, given half a chance.

"The human-wildlife interaction does not always have to be a disaster."