Beaver dam on the Spring Creek Nature Trail in The Woodlands, Texas. Trappers reduced beaver numbers to around one hundred thousand by the turn of the twentieth century. Today it is estimated their numbers have rebounded to approximately 15 million. Although they are not currently at risk of extinction, it is estimated that at one time 60 Million to 400 million swam in North America’s rivers and ponds. Beavers are the engineers in nature and provide value services to ecosystems. Just as forests pull carbon from the atmosphere and sequester it in wood, beaver ponds lock up carbon in buried sediment.