The Everglades, a vast and unique subtropical wetland ecosystem in South Florida, spans over 1.5 million acres. This intricate mosaic of sawgrass marshes, freshwater ponds, prairies, and forested uplands supports an extraordinary range of plants and animals. It also recharges the Biscayne Aquifer, providing drinking water for millions of Floridians. Despite its ecological significance, this globally recognized ecosystem faces numerous threats.
Changes to Water Management
Historically, the Everglades was characterized by a slow, shallow sheet flow of water originating from Lake Okeechobee, moving southward towards Florida Bay. This natural sheet flow, often only inches deep, spread across a wide expanse, shaping the unique “ridge and slough” landscape and its diverse habitats. Humans began altering this natural system in the late 1800s, primarily for agriculture and urban development.
Extensive engineering projects, including canals, levees, and drainage systems, were constructed to drain wetlands and control floods. These modifications significantly reduced the Everglades to about half its original size and fragmented the remaining ecosystem. Canals like the Miami, Hillsboro, and North New River diverted large volumes of freshwater eastward to the Atlantic, decreasing flows to the southern Everglades and Florida Bay.
This disruption of the natural flow has created areas of both excessive drought and unnatural flooding. Parts of the Everglades now receive too little water, leading to dry conditions that can cause peat soil loss and more frequent, intense fires. Other areas experience unnaturally high or pulsed water levels, which can degrade habitats and disrupt the delicate balance of wet and dry cycles. This alteration impacts native plant communities, such as sawgrass, and reduces populations of animals dependent on specific water levels and flow patterns, including wading birds and alligators.
Chemical Contamination
The Everglades ecosystem, naturally adapted to low nutrient conditions, is highly sensitive to chemical pollutants. Excess phosphorus, primarily from agricultural runoff and urban wastewater, has degraded water quality. This nutrient overload promotes the growth of non-native plants like cattail and leads to harmful algal blooms.
These blooms and non-native vegetation suffocate native sawgrass, alter the ecosystem’s chemistry, and disrupt the food web by reducing dissolved oxygen. This leads to changes in native plant communities and impacts areas where wading birds feed.
Mercury also poses a threat, entering the ecosystem mainly through atmospheric deposition from sources like coal-fired power plants. Once deposited, microorganisms convert it into methylmercury, a highly toxic form. This methylmercury then undergoes biomagnification, accumulating in increasing concentrations as it moves up the food chain. Top predators such as panthers, alligators, and wading birds can accumulate toxic levels of mercury, impacting their health and reproduction. This accumulation also poses potential risks to human health through the consumption of contaminated fish from the ecosystem.
Non-Native Species
Non-native, or invasive, species pose a threat to the Everglades, often introduced through accidental escapes from the pet trade or intentional releases. These species outcompete native flora and fauna, disrupt ecological balances, and alter habitats.
The Burmese python is a prominent example, having established a breeding population that has decimated native mammal populations across the Everglades. Studies have documented dramatic declines in native mammal populations, including raccoons, opossums, and bobcats, in areas where pythons are established. These large constrictors prey on a wide variety of birds, mammals, and even alligators, lacking natural predators in the ecosystem.
Melaleuca trees, introduced for landscaping and drainage, are fast-growing and outcompete native vegetation, forming dense stands that alter water flow patterns. Their presence also increases the risk and intensity of wildfires, further degrading habitats. Brazilian pepper, another invasive plant, forms monocultural thickets that reduce biodiversity and diminish the quality of native wildlife habitat.
Impacts of a Changing Climate
Broader climate shifts exacerbate existing vulnerabilities in the Everglades. Sea level rise is a concern, with projections indicating a substantial increase along South Florida’s coastline.
Rising ocean levels push saltwater inland, causing saltwater intrusion into freshwater marshes and aquifers, which compromises freshwater-dependent species and habitats. This intrusion threatens the Biscayne Aquifer, a primary source of drinking water for millions, and transforms freshwater ecosystems into saline environments, altering coastal habitats.
Altered rainfall patterns, including more intense rain events followed by prolonged droughts, disrupt the delicate water balance essential for the Everglades. Such changes affect water availability and natural cycles, stressing native species. Increasing temperatures also contribute to the degradation of the ecosystem. Warmer conditions can stress native species, potentially altering their breeding patterns and increasing the frequency and intensity of wildfires. These fires, while a natural part of the ecosystem, become more destructive when combined with drier conditions caused by altered water management and climate change, further degrading habitats.