The earth’s seas and lands are linked together by an intricate web of rivers and estuaries. The way we manage our lands, rivers and oceans impacts all living creatures in this web.

As a global leader in land and water conservation, The Nature Conservancy is demonstrating comprehensive, integrated approaches for managing land and water to benefit people and nature.

A Valued Resource Under Threat

The way we grow food and manage our urban and rural landscapes is having a significant impact on oceans. Fertilizers used in agriculture and on lawns, along with inadequately treated human and animal waste, flow downstream through rivers to estuaries and coastal marine areas, where they are contributing to a dramatic increase in algal blooms.  When these algal blooms die off and decay, they remove oxygen from the water and create “dead zones” that disrupt entire ecosystems.

Water pollution affects not just coral reefs, seagrasses, fish and shellfish, but also the human communities along the shore that depend on healthy ecosystems for their well-being and prosperity. 

Estuaries and coastal and near-shore habitats are an essential part of many people’s food and economic security:

• They support shellfish and associated economies, as well as other marine life;
• They serve as nurseries for many fishes that are harvested in the sea; and
• Estuaries and their associated wetlands also serve as buffers that absorb wave energy and rising tidal waters during storms. 

The Millennium Ecosystem Assessment labeled dead zones (eutrophication) as the second most pressing environmental problem after climate change. This threat is likely to continue to increase, given the rise in human populations and growing demand for food and bio-fuels. This, combined with rapidly increasing coastal populations in both developed and developing countries, places our rivers and seas at great risk if we don’t act now.

The combination of their delicate ecological balance and their attractiveness for human settlement has resulted in coastlines, near-shore habitats and estuaries being highly impacted by human activities.

Human-induced threats to these valued ecosystems include:

• Altered flow regimes: Dams and water withdrawals have decreased the amount of fresh water reaching the seas and increased salinity in estuaries and river mouths, the “nurseries” of the sea. Such alterations have dire impacts on oyster reefs, seagrass beds, mangrove forests and fish populations. Additionally, dams and levees obstruct pathways for migrating fish, keeping them from their spawning grounds.
• Water pollution: Nutrients and toxins are washed into our rivers and oceans, affecting marine life and placing human populations at risk. Drinking water and beaches are contaminated, impacting human health and requiring costly treatment and clean-up. Fish consume the pollution, with detrimental effects to them and to other species, including humans, who depend on them for food.
• Altered sedimentation patterns: Activities on land that accelerate erosion and sediment movement, or dams that stop the natural delivery of sediment to coasts and estuaries can result in declining habitats. In some areas deforestation, agriculture and land development leads to excessive sediment runoff. This excessive sediment clouds the waters and blocks sunlight from reaching seagrasses and smothers ecosystems like oyster reefs and coral reefs. Starving marshes and wetlands of sediment has contributed to the decline of shrimp fisheries in places like Mozambique where these habitats were an integral part of local livelihoods as well as ecosystems. 

The Nature Conservancy is working to abate these threats by working with partners on the ground and in the water. We are also working to develop and facilitate the implementation of integrated place-based and policy-based solutions that will have far-reaching conservation impacts.

Nature picture credits (top to bottom, left to right): Photo © Natalie Fobes (Washington Estuary); Photo © Alan Eckhart (development along Chesapeake estuary).