Scientists have long dreamed of regenerating extinct animals — a dream that is now reality thanks to advances in molecular science and genetic techniques. However, the cost, value, and significance of such efforts have always been questionable.

Freshwater ecosystems around the world are under intense pressure owing to a warming climate, pollution and declining biodiversity. Indeed, some 35 percent of wetland areas were lost between 1970 and 2015 — a rate three times faster than deforestation.