Getting around on market day along the muddy border between the Dominican Republic and Haiti is almost impossible for those unfamiliar with the art of dodging the trucks, motorcycles and bicycles swerving amid the messy piles of products scattered all over, and weaving among the hundreds of people coming and going between the two countries. It is also impossible to make your voice heard, so it is important to step carefully, to avoid falling underneath the crowd.

Around noon, the main business is concluded, to judge by the lines of men and women who, carrying loads on their heads, mingle with the vehicles, walking slowly and carefully across the border through the mud, puddles and sometimes knee-high water.

The authorities "are looking into how to move this market to a safer spot", said Yanelys Díaz, assistant to the mayor of Jimaní, a town of 14,000 on the border with Haiti and the capital of the province of Independencia in the south-west of the Dominican Republic. Díaz admitted that the site was a fertile breeding-ground for epidemics of cholera, malaria and dengue fever. "That has to be fixed," he told IPS.

Cross-border trade here has been squashed into a small, waterlogged area by the flooding caused when Lake Azuéi, on the Haitian side, overflowed. The water flooded most of the administrative buildings, and hundreds of people were affected by the drop in trade.

Local residents say that, up to 2007, Lake Azuéi only extended around 500m into Dominican territory. But it currently extends nearly 2km into this country, right up to the road that runs across the border. Haiti is the Dominican Republic's second-largest trade partner, after the US. The two countries share the island of Hispaniola.

Despite the adverse conditions, business goes on, a Dominican exporter of food products told IPS. "There are good days and bad days for sales. But they haven't stopped, and they are done in cash, in US dollars or Dominican pesos," said the businessman, who lost livestock and land when the lake grew.

Communities in the southern Dominican provinces of Independencia and Bahoruco share Lake Azuéi with Haiti. They also have Lake Enriquillo, the largest lake and the lowest point in the Caribbean. The economic life of the area flows around these two lakes, which have been in grave danger for years.

For this country of 10 million people, the rise in the water level in Lake Enriquillo represents an environmental challenge with serious socio-economic repercussions, especially since climate change. Around 15,000 hectares of farmland and pasture have been underwater since then.

But people in the area fear the situation will become even more serious. Several studies indicate that the rising water level in both lakes could be an early sign of coming climate change and environmental modifications in the region over the next 20 or 30 years. By 2100, they forecast, the Dominican Republic could lose 14% of its territory as a result of rising sea levels.

"With respect to the origin of the phenomenon [of rising lake levels], there are different theories and studies, but the community does not have precise or official information," Adela Matos, project manager for World Vision, told IPS.

World Vision has a clinic in Jimaní, which forms part of the Enriquillo-Azuéi coalition, an alliance of producers, traders, labour unions, the Catholic Church and the local governments of Independencia and Bahoruco that was set up to find a solution to the problems caused by the swelling of the two lakes. "It's obvious that the development achieved in recent years has been delayed by this situation," Matos said.

Among the institutions that have studied the problem, Matos mentioned the Autonomous University of Santo Domingo, the National Institute of Hydraulic Resources, and private university research centres such as the Technological Institute (Intec).

The online Dominican daily, Acento.com, reported that the preliminary results of a study by experts from Intec and the City College of New York found that the rising water levels were due to "hydroclimatic change" and the warming of the oceans. According to the research team, global warming is causing greater evaporation in the oceans, leading to more intense cycles of evaporation and rainfall, and to the swelling of rivers and lakes. These conditions are combined with the unusual drop in evaporation from the lakes, which leads to a further rise in water level. The experts warned that this is happening in Lake Azuéi (known as Lake Sumatre on the Haitian side), at Lake Cabral in the Dominican Republic and in lakes as far away as China.

Local residents and institutions are worried. "We can't rule out the possibility that, because of the saturation of the soil and the deforestation already affecting the area, a natural phenomenon like a stationary storm or a hurricane could produce a tragedy of greater magnitude than the one in May 2004," said Matos. That month, the sudden flooding of the Blanco river caused by heavy rainfall claimed more than 500 lives and left 1,600 people homeless in Jimaní, according to figures from the National Emergency Commission. The flash flood took the town by surprise, because the riverbed was practically dry at the time.

In 2004, Lake Enriquillo shrank to its smallest size in history: 165km². But that very year it began to swell, reaching 333km² in 2009 – nearly 50% larger than five years earlier.

Matos described the social disaster caused by the unprecedented growth of the lake. "Unemployment, commercial sexual exploitation of minors, child labour, illness and violence are visible consequences of the loss of livelihood among the affected families, and pose a latent threat to the possibilities of development for these communities," she said.

While people in this part of southern Dominican Republic are waiting for government measures to address the pressing problem, experts point out that Lake Enriquillo has varied in size for centuries, and say the only option is to adapt to it, because the lake cannot be relocated.

With respect to the increasingly intense and recurrent drought and rainfall caused by climate change, they say the best way to adapt is by moving crops, livestock and families to safer areas. According to official figures, 70% of cities and towns in the Dominican Republic are located along riverbanks.