The meaning of ‘environments separated by the exigencies of distance’

The meaning of ‘environments separated by the exigencies of distance’

The passage below is from Fathoms: The World in the Whale Hardcover by Rebecca Giggs.

Before any threatened animal species tips into extinction, its populations often become divided into undamaged regions, inaccessible places, or environments separated by the exigencies of distance. Subsisting in reduced or partitioned territory, or with their numbers depleted because of a pathogen or vanishing prey, fewer mature individuals tend to encounter one another, less frequently. This is particularly true of creatures that are solitary in adulthood, or which spend an interval of their development living segregated from any pack, herd, or pod — as do many of the great whales. Just as deforestation, pollution, and the construction of roadways can accelerate the demise of larger creatures by erecting barriers between their populations, so, too, does defaunation amount to the fragmentation of liveable territory for parasites. When the numbers of a parasite’s host species change, and particularly if the host tips towards becoming an endangered species, then opportunities for parasites to migrate to new hosts, and to interbreed, lessen.

In this passage the bold-faced phrase is a mystery to me.

I think I do know the literal meaning of individual words of the part.

A certain endangered species become divided into undamaged regions...

If I were them, I would do the same.

A certain endangered species become divided into inaccessible places...

Right. They seem to have no other choice.

But...

A certain endangered species become divided into environments separated by the exigencies of distance...

What? I don’t get any meaning out of this sentence.

I think ‘Exigencies of distance’ means ‘urgent requirement in terms of distance.’

(Am I right?)

But about ‘environments separated by the exigencies of distance’, I cannot figure out what those ‘environments’ are about.

Thanks in advance.