Research & Policy

Measuring the Connection between Land Protection and Clean Water

The science is clear: protecting forests makes for clean water.  

Still, additional research is needed as the conservation community seeks a better understanding of how the extent, type, and location of protected forests impact water quality. 

With funding from the William Penn Foundation, the Open Space Institute (OSI) is conducting a three-year study to measure the connection between land protection and clean water that will help guide its work in protecting the Delaware River watershed. The study will consider a range of topics, including how much of a watershed needs to be forested to keep water clean; how the uses of unprotected land affect water quality; and the role of forest protection in avoiding future degradation of streams and waterways. 

The OSI assessment will be informed by scientific literature review; consultation with scientists and data modelers; and assessment of programs that fund forest conservation to maintain water quality outside of the Delaware Basin. 

“Everyone has the goal of clean water, but different strategies are relevant in different places. Our goal is to develop a better understanding of the role of land protection in protecting and achieving clean water,” explained OSI Conservation Research Director, Abigail Weinberg. “With limited dollars to spend on land protection throughout the conservation field, OSI is examining data and lessons learned in order to target land protection for clean water. This will inform our spending in and around the Delaware.” 

And according to Weinberg, with municipalities and counties across the east protecting or restoring land for water quality, there’s no shortage of programs to investigate. Some illuminating insights are emerging.

A Recipe for Clean Water    

A review of the literature found broad agreement that if 70 to 90 percent of a watershed is forested, streams are likely to retain good water quality, pointing to a clear role for land protection.  Yet even with protected forest covering a large portion of the watershed, findings show that the land use of the non-forested areas is also critically important. Clean water and healthy streams remain at risk if high intensity agriculture covers more than 10 to 30 percent of a watershed or if impervious surfaces like pavements and buildings cover as little as three percent. 

These findings point to the value of focusing land protection in watersheds where there is still some significant forest land, along with a number of other land use factors. In fact, forest protection mixed with smart land use and planning may be the best approach for maintaining clean water. But are these the only places where land protection is a relevant tool? What about in less forested landscapes where development and agriculture have more of an impact?

Healthy Bugs Indicate Healthy Waters

The science from OSI’s review suggests some interesting answers. Studies have found that clean streams with healthy communities of bugs that are sensitive to pollution can help to re-populate adjacent degraded streams once their water quality and instream habitats are restored.  

According to Weinberg, once a formerly degraded stream reaches acceptable conditions to support diverse communities of bugs, mayflies, caddisflies and other sensitive species return to the restored stream. This is only possible if there is a nearby clean stream with a healthy bug community.

Conservation Approaches for Cleaning Water and Keeping Water Clean Differ  

In conducting her research, Weinberg has also been struck by the different approaches that need to be used in different places. “Keeping water clean requires a different plan than cleaning water already compromised by pollutants. Still, there appears to be an important role for land protection in each scenario.”

For example, in the Chesapeake Bay, where nitrogen, phosphorus, and sediment running off the land have significantly degraded water quality, restoration managers are now considering forest protection as an important contributor to Bay restoration. . Reducing the amount of forest conversion to development through land protection will help to maintain water quality into the future and reduce the need for costly urban Best Management Practices (BMPs). 

The context in the Chesapeake is unique. Unlike the Delaware where the leadership of a private foundation and over fifty non-profits are focusing on maintaining clean water and restoring marginal waters, the driving force behind the Chesapeake restoration effort is a “pollution diet” defined by stringent federal regulations known as the Total Maximum Discharge Load (TMDL). To achieve this diet, the Chesapeake’s partners are focusing their efforts on implementing a variety of agricultural and urban Best Management Practices throughout the watershed. 

Enter Peter Claggett, Research Geographer with the U.S. Geological Survey at the Chesapeake Bay Program, who is leading a team of land use modelers to put a value on land protection.  Claggett attributes interest in land conservation to the history of sprawl development starting in the 1950’s and exacerbated by the recent housing boom in the early 2000’ss that raised concern about the impact of massive, rapid development on the loss of forests and farmland. 

“While protecting forests doesn’t offer an immediate reduction in pollution to the Bay, if forest land is lost to development, pollution will likely increase and the amount of restoration that has to get done later will increase,” offers Claggett.

A Better Understanding of Land and Water Connection  

The significance of integrating land protection into a federally-regulated TMDL project could be transformative. It could potentially open the way for much greater funding directed towards land protection. For example, Maryland alone, has spent an estimated $15 billion on pollution reduction activities but only spends a fraction of that on land protection. 

Using a model that compares future land use conditions with and without expected land protection, Claggett and his team were able to calculate the amount of avoided future pollution to the Bay that could be achieved through land protection by 2025. 

While Claggett’s modeling shows that, over the short-term, land protection won’t contribute significantly to achieving the overall pollution reduction goals for the Bay, to Weinberg, this finding is informative. “This work reflects interesting lessons about the model and its assumptions, including very low investments in land protection compared to restoration, the need to couple water quality BMPs with farmland protection, and the importance of evaluating the benefits of conservation over longer timeframes,” she explained.

Claggett and his colleagues are studying their approach and modeling in anticipation of revisiting the issue in the future. “We hope to eventually capture more subtlety in our models to get a clearer picture of how targeted land protection can achieve greater impact,” he said.   

Either Way, Protect Forests

Until then, Claggett is confident that land protection is critical for maintaining water quality in the Chesapeake Bay over the long term. “It’s clear that land protection matters, but it is harder to value over such a short time scale compared to restoration. As well, many restoration practices require perpetual and expensive maintenance. Existing forests are doing a lot right now and they don’t require any maintenance costs. That is an immensely underappreciated service.” 

What advice would Claggett offer for OSI’s work in the Delaware?The water quality in the upper Delaware is so good. You want to preserve that and you want to accommodate growth while minimizing the future conversion of forests and farmland to development. 

“If you look at streams, they are really sensitive to small amounts of disturbance. Even converting less than three percent of forests in a small watershed to lawns, buildings, and pavement can knock out some of the most sensitive water bugs that are present in forested streams. Where you start to get up to 15–20 percent pavement and buildings, it may never be possible to restore such streams to their previous conditions. The once-healthy streams may be gone forever.”

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