As job interviews go, it was brief. Deryk Engel walked into his PhD supervisor's office at the University of Wollongong 16 years ago to ask a question about his thesis. As the phone started ringing in the empty room he answered it.

"The lady on the other end wanted one of the other graduates who wasn't there and she said, 'Well, do you know anyone who does environmental surveys?' I said, 'Yeah, sure, I do.' "

That stroke of luck led Engel from an environmental science degree to a career surveying native animal populations in Queensland, Victoria and all over NSW. Within three months he had contributed to the preservation of local yellow-bellied gliders on the site of the proposed Tully millstream hydroelectric dam project. The dam was never built.

Every second environment-related job these days seems to be some form of consultancy, but Engel's is in one of the more interesting fields. Since 1991 he has watched, stalked, trapped and counted hundreds of native animal species, from birds to frogs and bats to snakes. He has set traps up trees for gliders at Eden; he has searched for bats under wharves on Sydney Harbour and in limestone caves near Molong; and he has braved a snowstorm chasing mammals at Tenterfield.

Engel's generalist environmental degree didn't automatically lead to this kind of work, but he remembers always being interested in animals. He doesn't have clear recollections of it, but he reckons accompanying his Anglican missionary father on journeys across the plains of sub-Saharan Africa as a child was a factor.

"I was born in Dodoma, in Tanzania, and we lived in Africa until I was about four. In Africa we were surrounded by megafauna: the big stuff like lions, giraffes, gnus and elephants.

"Then when we came home, we had aviaries full of birds and blue tongues [lizards] as well as cats and dogs. Later, I had frogs and pythons.

"I think my upbringing gave me an appreciation that we share the planet with other animals. There are some amazing wildlife species with incredible habits. There are birds that look peaceful, but then when you look into them you find they kidnap other species' chicks; and they have wives, but they go off and have affairs; and they have epic battles of survival."

One thing he has increasingly noticed is how tolerant and adaptable animals are toward us and our artificial environments, provided they have natural habitat to return to.

"On Lord Howe Island, native woodhens will walk into the pub and lift up the door mats looking for insects," he says. "Lord Howe is a volcanic island, so to them a pub is just another type of rock. Animals are incredibly adaptable and tolerant when they don't feel threatened."

These days, Engel runs his own consultancy, LesryK, and most of his work involves measuring ecosystems that will be affected by development - his clients include government departments, conservation groups and developers.

Engel says we sometimes forget a basic rule of ecosystems: that impacts on one species have a chain reaction.

"The sooty owl, which is a threatened species, faces additional threats when something like arson occurs in a national park, because it affects the habitat requirements of its prey, such as the greater glider," he says. "Whenever we clear land we are clearing something's habitat: its breeding hollows, nesting sites and foraging areas."

The species under threat are too numerous to mention specifically, he says, but generally the deteriorating water quality in rivers, lakes and wetlands is threatening frogs, fish and water birds - as well as platypuses - and the destruction of habitats is affecting countless woodland animals.

So how does Engel feel about all the attention being paid to climate change, while species extinctions don't seem to generate as much public concern? "Climate change acts as an umbrella: if you address issues surrounding climate change you benefit anything sheltered under it. Biodiversity is sheltering under that umbrella."

But what about the specific actions of greedy developers?

"Some developers are short-sighted and only look at their financial returns; they believe the more houses closer together, the better," he says. "I would say overall the dollar still rules, but developers are trying and there have been some big improvements. Many see the benefits in including green corridors and parklands. They might lose about 2 per cent of the maximum number of houses by preserving the most important habitats, but that cost gets spread out because the clientele really want to move there so they are happy to pay extra. In the end, the developer may even make more profit.

"Recently, I worked with one developer who used to have a bit of a scorched earth policy, who had completely turned around his approach within about four developments.

"I think we have to accept there is a need for urban expansion, because we have population growth. But there has to be a happy medium between total destruction and no development at all."

DERYK ENGEL

P POSITION Principal ecologist, LesryK environmental consultants.

P CAREER PATH Bachelor of environmental science, University of Wollongong. Has been an environmental consultant, ranger for the NSW National Parks and Wildlife Service and an environmental officer for the NSW Roads and Traffic Authority.

P GREEN VISION Development should be ecologically sustainable and not compromise native species and communities, particularly animals and plants under threat.