Scoop the Poop for Cleaner Water

This article was originally published in an abreviated version in the Fall 2026 issue of EarthCare Northwest, our quarterly member newsletter. Become a member today and receive our next issue. 

Each summer, harmful algal blooms become more common in our local waters, closing popular beaches and swimming spots at Lake Washington and Green Lake, among others. While these blooms are driven by many factors, including warming temperatures and nutrient pollution, they raise an important question: are there everyday actions that can help? 

One possible contributor is something many of us encounter every day: pet waste. 

Scientists have long known that excess nutrients, especially nitrogen and phosphorus, act like fertilizer. When too many of these nutrients wash into streams, lakes, and Puget Sound through stormwater runoff, they can fuel excessive blue-green algae growth, also called cyanobacteria. As algae die and decompose, they consume oxygen from the water, creating conditions that can stress fish, aquatic invertebrates, and underwater vegetation. 

The Washington Department of Ecology identifies excess nitrogen from human activities as a major factor contributing to declining water quality and low oxygen levels in Puget Sound. While wastewater treatment plants are the largest human source of excess nitrogen, they are not the only one. Stormwater carries nutrients from many sources across the landscape, including fertilizers, organic debris, and animal waste. 

Research has shown that dogs can contribute meaningful amounts of nitrogen and phosphorus to natural areas through urine and feces. A 2022 study in Belgium estimated that dogs deposited enough nutrients in some urban natural areas to influence plant communities and potentially slow ecological restoration efforts. The researchers recommended removing dog waste and considering nutrient inputs from dogs when managing sensitive habitats.

Photo by E. Bonilla, Canva

What scientists have not yet demonstrated is a direct link between pet waste and declining bird populations. 

However, there is a logical ecological pathway that deserves attention: 

Pet waste → nutrient pollution → algal blooms → loss of aquatic vegetation and oxygen → reduced habitat and food resources for waterbirds

At Birds Connect Seattle, our Neighborhood Bird Project has documented declines in several species of waterfowl and waterbirds over nearly two decades of community science. Species such as Gadwall (69% decline) and Brant (94% decline), which had previously been stable or increasing, have shown declines. We have also recorded fewer observations of many shorebird species in recent years. While these trends cannot be attributed to any single cause, they may reflect broader changes in wetland and shoreline habitat quality. 

Healthy aquatic ecosystems depend on underwater plants such as eelgrass and other submerged vegetation. These habitats provide food and shelter for countless fish, invertebrates, and birds. When nutrient pollution contributes to algal blooms, sunlight can be blocked from reaching these plants, and low oxygen conditions can further degrade the ecosystem. The Brant, an aquatic goose, relies on freshwater eelgrass beds for 80% of its diet, highly impacted by algal blooms. 

Brant | Tim Bowman | Audubon Photography Awards

That is why simple actions matter. Picking up after our dogs doesn’t just keep parks clean—it may also help reduce nutrient pollution before it reaches local waterways. Combined with restoring shorelines, protecting eelgrass beds, reducing pesticide use, and improving stormwater management, responsible pet ownership is one of many ways our community can help protect healthier habitats for birds. 

The science is still evolving, and more research is needed to determine exactly how much pet waste contributes to nutrient pollution in urban watersheds and whether it measurably affects bird populations. But reducing unnecessary nutrient inputs is a practical, low-cost action that benefits water quality regardless of their ultimate contribution. 

As our Neighborhood Bird Project continues to track long-term changes in Seattle’s bird populations, these kinds of everyday conservation actions become part of a larger effort to create healthier cities where both people and birds can thrive.