Healthy Reefs
Threat Indicators: Drivers of change
Drivers of change are both natural events and human activities that negatively impact or degrade the integrity and health of the Mesoamerican reef ecosystem (MAR). In this context, drivers of change are any threats or stressors that may result in reduced species diversity, richness and abundance; reduced habitat quality, quantity, and productivity (including critical habitats such as spawning, breeding and foraging sites); and altered key ecological processes, such as larval transport. It is generally difficult to distinguish natural disturbance from human disturbances on regional and global scales, since effects can occur from multiple sources and may have synergistic effects. These combined events and activities may have long term effects on ecological processes that may enable or hamper the reef’s ability to recover and persist.
Of paramount concern to coral reef health are (i) Disturbances affecting reef health have increased in scale, frequency, and intensity; (ii)Recovery to disturbance is being delayed or not observed at all; and (iii) Disturbances that were once acute in nature are now becoming chronic.
The primary drivers of change posing the greatest risk to Mesoamerican reef health and in need of management interventions are: unsustainable tourism, improper land use and agricultural practices, overfishing, and global climate change.
Unsustainable Tourism and Coastal Development
Tourism is the fastest growing industry in the MAR, and is considered the largest single threat by many stakeholders. Inappropriate coastal development (including the destruction of mangroves and other coastal wetlands and littoral forests, marine dredging and beach ‘renourishment’ projects, and loss of riparian forests) is a significant threat exacerbated by lack of enforcement of existing land use planning/zoning regulations, increasing population densities, and persistent rural poverty.
Improper Land Use and Agricultural Practices
The main threats associated with improper land use and poor agricultural practices in the MAR are direct loss of habitat, sedimentation, and contamination of fluvial and marine ecosystems with fertilizers, pesticides, metals and hydrocarbons. Agriculture is perceived as the main driver of land-based threats in the region, but is joined by urban and industrial development, aquaculture discharges, and atmospheric deposition. While industrial and agricultural activities may be located at a great distance from coastal areas, they still impact downstream coastal estuaries, lagoon, seagrass bed and reefs.
Overfishing
Many scientists consider overfishing by humans to be one of the primary causes of coral reef decline in the MAR. The problem with overfishing is simple; humans are overly successful as an apex predator and are fishing at all levels of the food web. As a result, fish populations have suffered a decline in population abundance (particularly of the larger/older individuals), reduced species diversity, loss of key functional groups and local extinctions of species.
Species at greatest risk in the MAR today include the snapper-grouper complex, reef fishes (including large parrotfish), queen conch, and spiny lobster. Traditionally exploited during spawning periods, snappers and groupers have declined dramatically from historic levels and several historic aggregations have disappeared in the MAR region. Other reef fishes have traditionally been an important source for food, but the intensity and frequency of fishing is increasing at an alarming rate and declines in fish abundance and catches are attributed to lowered populations, over-fishing, changing economic circumstances, illegal fishing, destructive fishing methods like gill nets, and lack of enforcement.
Global Climate Change
A widespread driver of change in the MAR is stresses associated with global climate change, particularly the likelihood of more frequent and intense coral bleaching events. Global warming is expected to have broad environmental and socioeconomic impacts. Consequences of global change could include decreased coral growth/reef accretion rates, loss of reef structure, increased bioerosion, increase in susceptibility to bleaching, disease, and hurricanes and increases in sea level rise. Thus, effective proactive management efforts will be needed to protect the coral reefs from additional anthropogenic stress which would compound these global effects, prevent recovery from acute disturbances, and further increase the probability that these reefs will experience significant loss of ecosystem structure and function.
- Key Threat Indicators
- Table of Threat Indicators
- Ranking Results —Threat Indicators (pdf version -65KB)
