Australia is debating whether or not to list koalas (Phascolarctos cinereus) as a threatened or endangered species, and one of the ideas for saving them is to build tunnels to help the marsupials cross under roads without being killed by cars and trucks.

We're used to thinking about koalas living in trees, but they spend enough time on the ground that vehicles pose one of the major threats to the species. In the state of Queensland alone, 4,500 koalas were struck and killed by cars between 1997 and 2009.

Roadways are just one of the dangers the animals face as their populations are in dramatic decline. Other threats include drought, forest fires and excessive heat from climate change; deaths from dog and cat attacks; habitat loss and fragmentation; and, as I wrote two years ago, a deadly, AIDS-like retrovirus as well as chlamydiosis infections.

Although no firm numbers exist for koala populations across the Australian continent (estimates range from 35,000 to 100,000), the animals have declined as much as 80 percent in areas such as the Gold Coast during the past 10 to 15 years. (On the other hand, they are overpopulated in a few other regions, such as Kangaroo Island, although they never lived on that island before white settlers brought them there a century ago.)

This week, following 10 months of study, Australia's Senate Standing Committees on Environment and Communications released a list of 19 recommendations to help save the koala. Among them: lowering highway speed limits near koala habitats; building either koala-proof fences, or bridges and the aforementioned tunnels to help the animals cross over or under other roads; controlling the population of wild dogs, which killed at least 954 koalas between 1997 and 2009; identifying key locations for koala conservation; and putting more money into koala research, including the quest for new vaccines. The committee's full report is here.

Environment Minister Tony Burke told the Australian press this week that "koalas are an iconic Australian animal. They hold a special place in the hearts of Australians."

But although the Senate committee also acknowledged the "surprising" level of passion that koalas engender, not everyone in the country is pro-protection. Much as U.S. businesses are saying that protecting the dunes sagebrush lizard (Sceloporus arenicolus) under the Endangered Species Act would threaten oil jobs, Australian businesses argued to the committee that protecting the koala would cost "tens of thousands" of construction and mining jobs.

Burke said he will make a decision about listing the koala as a threatened species under the nation's Environment Protection and Biodiversity Conservation Act before the end of 2011.

Photo via Wikipedia. Used under Creative Commons license