JOHANNESBURG, (Reuters) – The World Bank issued the first ever wildlife conservation bond in the world, raising $150m to support efforts to save the South African endangered black rhinos. This was announced in a statement by the bank on Thursday.

According to the bank, the five-year rhino bond issued Wednesday will return investors returns based upon the growth rate of black rhino populations in South Africa’s Addo Elephant National Park and Great Fish River Nature Reserve (GFRNR).

Investors would see an average return of 3.7% to 9.2% over five years if there is an increase in population. If there was no increase in black rhino populations, investors would not get any return.

The endangered rhino species, black rhinos, is a two-horned rhinoceros that can only be found in Africa. According to Save The Rhino International (a non-profit organization based in London), their numbers plummeted by 96% between the 1970s to 1990s to less than 2,500. This was due to poaching for their ivory in China and Middle East.

Later, extensive conservation efforts led to an increase in the number of rhinos to between 5,500 and 5,000, according to Save The Rhino’s website.

The South African black rhino population accounts for about half of Africa’s total, according to World Wildlife Fund (WWF), an international non-governmental organization.

The statement was made by David Malpass, President of the World Bank Group. He stated that the pay-for success financial structure “protects endangered species” and strengthened South Africa’s conservation efforts through the use of the infrastructure and track record in capital market investments.