The BBC's Cathy Jenkins: "Poaching is making a comeback"

The Tsavo National Park count is taking place at a crucial time for elephants and traders in ivory.

Next month a meeting of CITES, the Convention of International Trade in Endangered Species, will review a decision made in 1997 which allowed three southern African countries to legally sell ivory.

Kenya hopes to use data from the survey to fight any further relaxation of the rules which permit Zimbabwe, Botswana and Namibia to sell a limited amount of ivory to Japan.

A clause in the CITES decision says ivory sales will be stopped if any country can show that the limited trade is adversely affecting its own elephant population.

Poaching increase

The survey has been costly and complicated for Kenya with dozens of volunteers counting elephant numbers as accurately as possible from the air.

Paula Kahumbu, of Kenya Wildlife Service: "Elephants a keystone species"

But Kenya Wildlife Service believes the work will be essential. It believes the limited legal ivory trade is encouraging illegal poaching in Tsavo National Park.

Park worker Daniel Woodley said: "Over the last 18 months we have noted an increase in poaching - from losing less than 50 a year up to about 100 a year.

"I suspect it is in anticipation of the ban being lifted rather than supplying the limited trade that is already going on."

Between 1988 and 1997 there was a worldwide ban on the ivory trade to try to protect an elephant population which had suffered drastically at the hands of poachers.

In Tsavo elephant numbers had reduced from 45,000 in the 1960s to about 2,000.