Final answer:
A species with market value is likely to be overexploited, leading to endangerment or extinction, as seen in the cases of giant bluefin tuna and black rhinos. Effective conservation measures are needed to reduce both demand and illegal trade.
Step-by-step explanation:
Whenever a species has market value, it is likely to be overexploited, which can potentially lead to its endangerment or extinction. Examples of overharvesting and illegal trade in high-value species include the illegal harvesting of giant bluefin tuna and rhino horn trade after the ban of rhino products. The thriving illegal trade often undermines the conservation efforts, leading to declines in population; for instance, the black rhino became extinct in at least 18 African countries following a trade ban. Conservation measures need to address not just the prohibition of trade but also need to reduce demand and regulate legal and illegal trade to protect species from overexploitation.