Wildlife of
Réunion

Primary Threats

• Invasive plants and animals are a primary driver of native biodiversity decline on Réunion. Invasive plants (e.g., aggressive shrubs/vines and fast-growing trees) overtake native forest understorey and regeneration, transforming habitat structure. Invasive predators such as rats and feral cats predate on endemic birds, reptiles and invertebrates; invasive insects can disrupt pollination and forest dynamics. Control is especially challenging in rugged terrain (cirques and steep remparts) and in lowland fragments where reinvasion pressure is constant.
• Most remaining native habitats are confined to uplands and protected interiors; lowland and coastal ecosystems (including dry forest, wetlands, and coastal vegetation) have been extensively cleared or fragmented by settlement, tourism facilities and past agriculture. Ongoing land conversion and edge effects reduce connectivity between native patches, increasing vulnerability to invasive species and fire, and limiting recovery of endemic plants and fauna.
• Population and economic activity are concentrated along the narrow coastal ring, driving expansion of housing, commercial areas and associated services. This increases pressure on the last low-elevation natural habitats, accelerates fragmentation, and raises disturbance (noise, light, pets) near sensitive sites. Urban growth also increases stormwater runoff and pollution loads to lagoons and nearshore reefs.
• Major roads (including coastal routes and interior access roads), slope stabilization works, and tourism infrastructure (viewpoints, trails, facilities) can fragment habitats and create corridors for invasive species. Road widening and new transport projects can impact remaining lowland habitats and increase wildlife mortality (vehicle strikes) for birds and reptiles, while construction on steep volcanic terrain can drive erosion and sediment delivery to streams and reefs.
• Land-based runoff (sediments from erosion, nutrients, pesticides where used, and urban wastewater/stormwater) affects rivers, lagoons and coral reef areas along the west and south coasts. Marine litter and plastics also accumulate on beaches. On steep catchments, heavy rainfall events can rapidly move pollutants and sediments downstream, stressing seagrass/reef-associated ecosystems and coastal fisheries.
• Warming and shifting rainfall patterns threaten montane cloud forest and high-elevation endemics that have limited ability to move upslope. More frequent/intense droughts and heat can increase wildfire risk in upland heath/forest margins and degrade lowland remnants. In the marine realm, warming and marine heatwaves raise the risk of coral bleaching and disease, while sea-level rise and stronger storms increase coastal erosion and lagoon impacts.
• High visitor use in iconic landscapes (Piton de la Fournaise, cirques, popular trails) can cause trampling, erosion, disturbance to nesting seabirds, and off-trail spread of invasive seeds. Recreational pressure in lagoons (boating, snorkeling) can physically damage sensitive habitats if poorly managed, and nighttime lighting near coasts can disorient seabird fledglings.
• Alteration of hydrology and river channels (flood protection works, bank hardening, water abstraction in some catchments) changes sediment and flow regimes that native freshwater biota depend on. Fire regimes have also been modified: human-caused wildfires in upland/edge areas can convert native vegetation to invasive-dominated communities and increase erosion on volcanic soils.
• While large-scale expansion is limited by terrain, agriculture (notably sugarcane in lowlands and horticulture in suitable areas) has historically displaced native vegetation and continues to compete for space in coastal/low elevation zones. Agricultural edges can facilitate invasive species spread, and agrochemical runoff can affect downstream aquatic and coastal ecosystems.
• Local pressures include extraction/collection impacts such as overharvesting of certain coastal resources in accessible areas and localized depletion of reef-associated species where enforcement or compliance is variable. Freshwater abstraction in some basins can also reduce ecological flows, especially during dry periods.
• Fishing pressure in nearshore waters can reduce reef fish biomass and alter food webs, particularly in easily accessed coastal areas. While management exists through marine protected zoning, enforcement and compliance challenges can persist, and illegal or unreported take can undermine recovery.