Wildlife experts and officials from around 30 governments will gather next week in Botswana to confront the threat that wild elephants could be heading for extinction, due in part to Chinese demand for ivory.

Between 420,000 and 650,000 African elephants survive, but more than 100,000 have been killed in the past four years, according to a study published in the US Proceedings of the National Academy of Sciences journal.

The African elephant is rated as "vulnerable" on the International Union for Conservation of Nature index, while the Asian elephant is rated as "endangered" -- a cause of serious concern.

"It is not sustainable as, if trends continue, the elephant population could be at risk of extinction especially in central Africa where we see the greatest amount of poaching," said Heather Sohl, a senior adviser with conservation group WWF.

"What we need to see is governments implementing the actions they have agreed."

The African Elephant Summit will be held in Kasane on Monday to follow up on a 2013 meeting when 30 countries adopted a set of urgent conservation measures, including a call to unite against poaching and for improved criminal prosecution.

On Wednesday, the Conference on Illegal Wildlife Trade (IWT) will then meet to focus on the trafficking of all threatened species -- an illegal trade worth $19 billion a year, according to the International Fund for Animal Welfare.

In one graphic example of declining numbers, the TRAFFIC wildlife trade monitoring group reported that between 2007 and 2013 the elephant population in the Tanzanian reserve of Selous dropped from 70,000 to 13,000.

"Over the past few years, I have documented with regret the slow retreat of elephants from habitats they were rapidly repopulating," said Mike Chase, director and founder of Elephants Without Borders.

"The threat of local extinction feels very real."

- Criminal networks -

All experts agree that elephant culling is organised by international criminal networks that supply the illegal ivory market, mainly in Asia, with some profits thought to fund regional conflicts and militants.

Ivory is reportedly bought at $100 per kilogram ($45 per pound) from poachers, and sold for $2,100 in China, the main market.

"China holds the key to the future of elephants," said Iain Douglas-Hamilton, founder of Kenya-based Save the Elephants.

"Without China's leadership in ending demand for ivory, Africa's elephants could disappear from the wild within a generation."

Under international pressure, Beijing in February made the small -- and largely symbolic -- gesture of banning ivory imports for a year.

"(This is) a significant step in the right direction, signalling a growing realisation in China of the role they play in the demand for ivory," said Douglas-Hamilton.

"It is hugely optimistic sign, but much more action is still needed."

In central Africa, more than 60 percent of forest elephants, a local subspecies, were slaughtered in the last decade.

"The analysis confirms what conservationists have feared: the rapid trend towards extinction -- potentially within the next decade -- of the forest elephant," said Samantha Strindberg of the Wildlife Conservation Society (WCS) and one of the authors of a study of the forest elephant.

Campaigners stress that more talking and more idealistic pledges this week will not be enough.

"Saving the species requires a coordinated global effort in the countries where elephants occur, all along the ivory smuggling routes, and at the final destination in the Far East," said Fiona Maisels, co-author of the WCS study.

The elephant has survived better in South Africa and Botswana than further north due to poachers concentrating on killing rhinos, whose horns are prized in Asia for their supposed medicinal qualities.

Officials said protecting the rhino will also be high on the agenda at the IWT conference in Kasane.