Elephants in one of Africa's largest and oldest reserves are feared to be wiped out by 2022, and this is because of poaching and mining, the World Wildlife Fund (WWF) says.

Selous national park in Tanzania is a world heritage site and is the oldest in Africa, boasting about 110,000 elephants 40 years ago. But it has already lost an average of about 2,500 elephants a year since 1970.

Now, the number has gone down to a critical 15,000 count, according to the latest census.

"The population is at a historic low, and urgent measures are required to protect the remaining animals and return the population to a stable and sustainable size," said WWF in a recent study.

According to the report, the reserve had lost 90 percent of its elephants over the last 40 years, and if the trend continues, they could "vanish from Selous by early 2022."

The group also said that "industrial scale poaching," which is driven by the increasing demand for ivory from Asian countries--China being one of them--was the reason behind depleting numbers in the reserve.

Other industrial activities that should also be put to end are oil and gas exploration and mineral extraction, which are continuously threatening other species in the park such as lions, leopards, wild dogs, buffalos, hippos, crocodiles and 400 bird species.

According to WWF, action has to be taken both in Tanzania and in Asia.

"The demand from the Asian countries, China being a key one, Thailand and others, are a key and we are working with the Chinese government alongside the other Asian countries that are involved in the illicit trade and transit of the illicit trade," Fred Kumah of the WWF said in a report in BBC.

Tanzania's new president has pledged to tackle the corruption that persists and continuously drives the illegal trade of ivory.

Selous national park in southern Tanzania was named a World Heritage Site by UNESCO in 1982. But in 2014, records showed that an average of six elephants were being killed every day for their ivory, and for this the reserve had been included in the list of "World Heritage Sites in Danger."