DNA损伤（DNA damage）。
Minimizing the environmental damage that new roads cause is generally regarded as a good thing. But to do that, it helps to understand just how new roads cause the damage of which they are accused.
Recently, a group of researchers led by Dr Gonzalez conducted an experiment which shows what ecologists have long suspected, but never been able to prove: that immigration is good for the health of animal populations.
A road destroys only a small part of the habitat it traverses, and thus annihilates just a few local populations of creatures. So the argument that road-building itself is bad for biodiversity is not self-evidently correct. Those who nevertheless hold this view usually point to a piece of ecological theory called "meta-population dynamics". This says that apparently separate local populations of animals are, in fact, parts of much larger populations connected via migration.
According to this theory, when a local population flounders &mdas
A. They destroy plants along the roads.
B. They cause damage to nearby forests.
C. They make some natural habitats unlivable.
D. They endanger many species.
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