Leonardo DiCaprio--Here is a celebrity that has the intelligence to know a real cause from a phony one.

Leonardo DiCaprio, a WWF board member, fixes a camera trap on a recent visit to Nepal. Photograph: Jan Vertefeuille/WWF

Leonardo DiCaprio made a million-dollar commitment to conserve tigers today as the leaders of Russia, China and a dozen Asian nations struggled to put together a finance package to double the wild population of the endangered predator.

The star of Titanic, The Aviator and Blood Diamond announced plans to donate part of his fortune through the environment group WWF to fund anti-poaching efforts, habitat protection and campaigns to raise awareness about the plight of the animal.

"Illegal poaching of tigers for their parts and massive habitat loss due to palm oil, timber and paper production are driving this species to extinction," said DiCaprio. "If we don't take action now, one of the most iconic animals on our planet could be gone in just a few decades."

DiCaprio is in St Petersburg for a tiger summit hosted by Russian president Vladimir Putin. The gathering of heads of state where tigers exist in the wild, including the Chinese premier Wen Jiabao, is the highest-level event ever staged to save a single species. Other donor countries such as Norway are also present although Britain has not sent a representative.

The strong demonstration of political will and celebrity support has not yet been matched by adequate funds to achieve the summit's goal of increasing the number of wild tigers from an estimated 3,200 today to at least 6,400 within 12 years.

The World Bank is trying to raise $350m from governments, institution and private donors to achieve this goal. The Wildlife Conservation Society said it would put $50m on the ground before the next year of the tiger in 2022.

NGOs said a stable, long-term mechanism was needed that would best be provided through the Redd-plus scheme to protect forests with carbon financing.

"We know how to save tigers. The problem is we don't sustain it. We fund conservation for a few years and then it tails off," said Eric Dinerstein, chief scientist at WWF. "We have to find sustainable financing."

Stanley Johnson, of the Convention on the Conservation of Migratory Species of Wild Animals, said $350m over five years was "chicken feed".

"If we can mobilise $80bn to save Irish banks, then surely a tiny fraction of that can be mobilised to save tigers," he said.