Each year, roughly 350 million pounds of nitrogen flow into the Chesapeake Bay. Unless we change current practices, a growing population and wasteful land use patterns will mean even more nitrogen pollution. The majority of nitrogen comes from five sources:

• Emissions of nitrogen oxides and ammonia from vehicles, industries, agriculture, electric utilities and other sources
• Chemical fertilizers applied to agricultural, urban, and suburban lands
• Treated wastewater discharged from industrial facilities and municipal wastewater treatment plants
• Manure from agricultural lands
• Septic systems that treat household wastewater and discharge nitrogen into groundwater

Precipitation, snowmelt, and irrigation move nitrogen through groundwater and surface waters into streams, rivers, and lakes. This problem is exacerbated when developers, farmers, or others remove natural vegetative buffers along streams, allowing nitrogen to flow unimpeded into our waterways.

Excess nitrogen is the most serious problem facing the Chesapeake Bay and the thousands of miles of local streams, creeks and rivers that drain its watershed. Nitrogen fuels the growth of algae, which block sunlight necessary for the growth of underwater grasses. When algal blooms die off, they decompose and consume oxygen, reducing the level of dissolved oxygen to a point that fish and shellfish can no longer survive. The result is an ever-increasing "dead zone" within the Chesapeake Bay and many of its tidal rivers.

Just as in the open Bay, the watershed's thousands of miles of streams and rivers are not immune to the impacts of excess nitrogen. Reduced oxygen levels in rivers and streams can diminish aquatic life, inhibit the ability of aquatic plants and animals to survive and reproduce, and cause fish kills.

The three greatest threats to water quality within the Bay watershed are nitrogen pollution, phosphorous pollution, and sediments. Like nitrogen, phosphorus can cause excess algae, blocking sunlight and reducing levels of dissolved oxygen. Excess sediment degrades water quality and damages critical habitats by blocking light and smothering plant and animal life.

Many of the conservation and restoration practices that help reduce nitrogen pollution such as streambank fencing, forest buffers, and winter cover crops also reduce excess phosphorus runoff and sedimentation. In addition, many of these practices have benefits to wildlife and can help sequester carbon, thereby helping to fight global warming. When targeting investments in cost-effective nitrogen-reduction practices, these ancillary will be considered.