Many populations are in decline due to shrinking habitats

The statement is - True.

Many populations of both the flora and the fauna on our planet are shrinking because of the loss of habitat. Even if all the other reasons are nonexistent, like the pollution and hunting/poaching for example, the loss of habitat will result in shrinking numbers in the populations of lot of species.

As a nice example we can take the polar bear. It is not a species that is affected by the humans in the way of hunting, or lose its habitat because of pollution, but because of the global warming, which is accelerated by the human activity, the temperatures in the tundra are rising, the summer is prolonging, so little by little the polar bear is losing its natural habitat. This loss of habitat is with a very quick tempo, the animal doesn't have enough time to adapt, so the polar bear populations are shrinking, and many of the individuals suffer from malnutrition. If this continues, they will lose most of their habitat, and the species will probably go extinct.