Wetlands are threatened world-wide because of alterations in local hydrology, water quality and "development" schemes. Many areas are experiencing unfavourable changes in vegetation and associated wildlife. Estimates of the remaining global area of wetlands range from 4.0 to 6.1 million square kilometres, of which around 2.64 million square kilometres occur in the tropics (World Resources 1990-91). The savannas are threatened by clearing and burning of the vegetation. This is often carried out by hunters as the resulting new shoots attract grazing animals.
In a local context, the most immediate threat facing the wetlands and savanna areas of the RBCMA comes from agriculture. Most of the adjoining land has now been cleared and drained for cattle grazing and cultivation. The nearby mennonite communities are amongst the most successful farmers in Belize.
This is similar to the pattern in mid-latitude regions: large areas of wetlands drained for agriculture and development. The US is thought to have already lost over 56% of its original wetland area, once 870,000 square kilometres. The Everglades in Florida, similar to the wetlands of Belize, for example, have seen the gradual replacement of marsh plants such as sawgrass (Cladium jamaicense) and sloughs (Eleocharis spp.) with the invasive cattails (Typha domigensis). This is thought to be the result of nutrient-enriched agricultural drainage waters entering the area. Equally, hydrological modifications to the wetland complex has deprived certain areas of freshwater, resulting in hypersaline conditions, increasing the level of stress on many organisms.
Changes to the local hydrology of a wetland affects both the flora and fauna. During particularly dry conditions experienced in the Rio Bravo area in 1994, migrant birds which usually spend many weeks in the RBCMA grounds instead quickly moved on. Sightings of large animals such as tapirs were also down, as many of the water holes in which they bathe and wallow dried up. Howler and spider monkeys were affected too, forced into greater contact with humans in their search for food.