EDMONTON -- A Canadian scientist plans to warn the world's policy-makers they can no longer ignore that the effects of climate change on a type of tropical forest are already forcing mass migrations of people.

"The tropics are not just the Amazon," said Arturo Sanchez, who has been invited to appear this week before a United Nations-sponsored climate change meeting in Marrakech, Morocco, to speak about the tropical dry forests of Central America.

The lush green carpet of the Amazonian basin is what leaps to mind when tropical forests are mentioned. But Sanchez says the dry forests -- where torrential rainy seasons alternate with a long arid season -- are the most endangered forest ecosystem in the tropics.

"Right now, only 40 per cent of the original extent remains," Sanchez said.

Much of the problem stems from centuries of exploitation. Soils in such forests are among the most fertile in the region and much vegetation has been plowed under.

Climate change has added a new threat -- drought.

Sanchez said 2013 was a normal year in the region. But the following year, the rain simply dried up.

"We had one of the worst droughts ever in Central America."

About 100,000 families were forced to pick up and move. Governments had to take emergency measures.

"It was insane."

Trees in huge swaths of forest simply dropped their leaves and went dormant. Productivity -- measured in the amount of carbon absorbed by the trees during respiration -- dropped in half.

As growing seasons shrink, so little fruit is appearing that monkeys are facing starvation. Social tension is also growing, said Sanchez, as residents suffer water shortages while tourist resorts irrigate their golf courses.

Sanchez doesn't hesitate to say the drought was caused, at least in part, by climate change.

"It was way beyond natural variability. We haven't seen that stuff in 100 years."

Despite the severe impact, research on dry forests is minuscule compared with that conducted in the rain forests, Sanchez said. Dry forests are also under much more pressure from economic development, he said.

The UN meeting, called the Conference of Parties, is to begin on Monday and lasts all week. Held yearly, the meetings are intended to bring policy-makers together to discuss the latest science and to come up with international responses to climate change.

The last one in 2015 resulted in the Paris agreement, in which the 196 countries attending agreed to a goal of limiting climate change warming to 2 C. The agreement has come into force after being ratified by 55 countries, including Canada, that represent 55 per cent of global carbon emissions.

Sanchez said he hopes the Marrakech meeting will result in similar progress on threats to tropical dry forests.

"Canadians need to realize that as we move ahead in the climate change era, we need to start taking international leadership. We need to start making contributions to a global understanding."