ROME (Thomson Reuters Foundation) – Countries most dependent on agriculture are also at high risk of experiencing changes in climate over the next 30 years and face the biggest costs in dealing with the effects of extreme weather, according to a global climate index published on Monday.

Sub-Saharan Africa is home to 17 of the 20 countries most economically reliant on agriculture in the world.

Of the 17, all but two are at "high" or "extreme" risk of experiencing changes in temperature and rainfall, and extremes such as drought and floods, according to the Climate Change Exposure Index.

These are typically countries whose governments lack the financial or technical resources to plan 20 or 30 years in advance, said Richard Hewston, principal environmental analyst at Verisk Maplecroft, a UK-based risk management company which compiled the index.

"They're dealing with droughts now, they're dealing with food security issues now, they don't have that capacity to be looking 30 years down the line," he told the Thomson Reuters Foundation in a telephone interview.