Frogs are considered to be good indicators of the environmental health of an ecosystem and declines in the numbers of species of frogs and the size of frog populations is generally cause for concern.
(Frogs; to be; good indicators of the environmental health of an ecosystem and declines in the numbers of species of frogs and the size of frog populations)
Frogs
to be
good indicators of the environmental health of an ecosystem and declines in the numbers of species of frogs and the size of frog populations