How are they trying to make koalas not endangered?

Koalas are not endangered.

The koala has been a protected species since earlier in the twentieth century, and this action has brought it back from the brink of extinction, a situation which was due to it being hunted for its fur. Koalas enjoy a quite healthy population in many parts of eastern Australia, although currently they are listed as "vulnerable" in southeast Queensland. Koalas are a protected native species and many things are being done or trialled to prevent their becoming vulnerable in other areas.

It is up to the individual state governments in Australia to determine how koalas are best helped. Trials have been done to build special passages (as mentioned above) for koalas to travel under roadways to reach feeding grounds. For many years, the Redland Shire (now city) of southeast Queensland maintained speed limits on roads for certain seasons of the year and times of the day, to minimise the risk of koalas been hit by cars. The trials were unsuccessful, and subsequently scrapped. More successful have been LED displays which light up as drivers approach: if the driver is travelling too fast for the koala zone, the sign conveys this information.

Other trials have seen the management of housing estates, where the keeping of domestic pets such as dogs is tightly controlled, to minimise danger to koalas. In some areas, eco-passages have been built for koalas and other native wildlife to safely cross over or under busy roadways.

Some housing developers try to "buy" government approval for large housing estates by including plans for koala hospitals to be built within their areas of planned development. Sometimes local governments will not compromise the safety of koalas with such a ridiculous scheme, and refuse approval for such housing applications. Research on koala needs is constantly being carried out, and other areas have koala and native wildlife hospitals anyway, seeing a need for such a facility with the increasing numbers of koalas being injured by cars, people or dogs.

Initially there were no koalas in Western Australia, and South Australia's population had been wiped out by the 1920s. This has now been reversed. Kangaroo Island off the coast of SA and isolated islands off Victoria's coast have actually seen an overpopulation problem due to these protected colonies. New colonies have been established in Western Australia, and the koalas are breeding quite successfully. Captive breeding programmes are among the most successful way to prevent koalas reaching "endangered" status.