Wetlands are unique ecosystems that exist at the interface of land and water, characterized by either permanent or seasonal water saturation. They develop through natural processes such as sediment accumulation, waterlogging, and the growth of specialized vegetation.

Wetlands are vital for aquatic ecosystems because they:

1. Facilitate Nutrient Cycling: Acting as natural biofilters, wetlands trap pollutants and recycle nutrients, helping maintain water quality.
2. Regulate Water: They buffer water levels and maintain soil moisture, reducing the effects of floods and droughts.
3. Provide Habitat: Wetlands serve as crucial habitats for a range of organisms, from microorganisms to plants and animals. For example, riverine floodplain wetlands support grasses and fish species, offering breeding grounds for aquatic life.
4. Sequester Carbon: Wetlands store significant amounts of carbon, contributing to climate change mitigation.

Regarding biodiversity conservation, wetlands:

1. Support Species Diversity: They host a wide array of organisms, including fish, amphibians, birds, and mammals. The Sundarbans mangroves, for instance, shelter the Bengal tiger and estuarine crocodiles.
2. Act as Migratory Stopovers: Wetlands such as Chilika Lake in India are essential resting and feeding sites for migratory birds, including the endangered Siberian crane.
3. Mitigate Environmental Extremes: By regulating floods and droughts, wetlands ensure the survival and stability of various species.
4. Preserve Genetic Diversity: Wetlands maintain unique genetic resources that support species adaptation and resilience. Peat bogs, for example, harbor specialized plants like sphagnum moss and animals like the bog turtle.

The destruction of wetlands directly threatens biodiversity. For instance, draining wetlands in Siberia has adversely affected Siberian crane populations, while degradation of the East Kolkata Wetlands endangers local fish species and migratory birds.

Thus, conserving wetlands is essential for achieving Sustainable Development Goals related to clean water [SDG 6], life below water [SDG 14], and life on land [SDG 15]. International initiatives like the Ramsar Convention of 1971 provide frameworks for the sustainable use and protection of wetlands, underscoring their ecological and environmental significance.