Elephants are paying the price for Asian economic success.

Because more Asian people are living in Africa, especially Chinese, there is an increased demand for the sex organs of elephants which in some Asian cultures is considered an aphrodisiac.
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Phrases: 

under severe threat: in great danger, in this case of extinction

dwindling herds:  disminuir (dwindle), manada (of elephants)

a by-product of: in this context, a secondary and sometimes unexpected result
to pay their respects: presentar sus respetos
prompted: instigated

smugglers: contrabandista