Author Archive: Andrew Leahy

For the Whole Stream: Riparian Buffers

Part 1: Upstream

This blog is the first installment of a new series called the Horn Farm Ecosystem. Through monthly articles, we’ll walk the land in writing: visiting the forests, regenerative fields, and ecological action sites of the Horn Farm Center to explain our stewardship work, uplift nature, and inspire love for the land. To learn more about the Horn Farm Ecosystem blog series, check out our February 17th, 2023 newsletter.


Whether you’re gathering for a class at our corn barn or whooshing by on Rt. 30, there’s a site at the Horn Farm Center that can’t be missed. Look east of the farmhouse, beyond the community garden plots, and you’ll see an expanse of tree tubes covering nearly 8 acres of land formerly dedicated to annual monocropping. Dotting the landscape, a twiggy menagerie: thousands of saplings planted between 2020 and this past summer eagerly waiting to outgrow their enclosures and bring large vegetation back to the land. In a time frame that seems tedious to us but a snap for nature, the likes of American hazelnut, sycamore, black and sandbar willow, various dogwoods, and more will cover this swath: a new forest born out of a willful overtaking. We’ve convened hundreds of community groups and volunteers over three years to facilitate this afforestation–or creation of a forest where there wasn’t one before–committing hundreds of hours and thousands of trees to just a fraction of our 186 acres, but why?

A sapling outgrowing its tree tube in the Horn Farm’s 8-acre riparian buffer, October 2022.

It’s of little contention that diverse trees (in tree-favoring environments) are a good thing, especially in a bioregion like ours, which now contends with a centuries-long legacy of agricultural clear-cutting alongside concerning air quality compared to the rest of the state. But there’s more to the story of the 15,000+ trees that have taken residence in our soils since we turned our attention to riparian health.

Venture out to the spot mentioned above and you’ll notice that the tree tube procession parallels a deep trench carving its way down the hillside. This is a human-made seasonal stream corridor, originally dug to drain water from bordering croplands. The eroded cut deposits into a natural creek—Kreutz Creek for York County readers—which then meanders east before emptying, like so many of our regional waterways, into the Susquehanna River. This downstream connection is the primary impetus for our undertaking. What we’re building is a riparian buffer.

What is a riparian buffer?

Picture: a lush array of grasses, shrubs, and trees snaking along both sides of a freshwater stream. This is a riparian buffer. The word “riparian,” from the Latin “streamside,” describes the area’s natural character: a transitional zone between the land and the waters of a river, lake, or stream, sometimes taking the shape of a wetland. “Buffer” designates the riparian area’s function in absorbing the impacts of adjacent land uses on the water. Across PA, riparian buffers have grown increasingly popular (and imperative) in agricultural fields, yards, commercial sites, and along roadsides: any place where the proximity of human activities to critical waterways is apparent and felt. Each riparian planting provides a host of benefits for water quality, soil health, and the surrounding ecology.

Simply put, the presence of trees, shrubs, and other vegetation along a waterway provides natural protection for the water and the life it carries.

Riparian buffers act like safety nets for streams, rivers, and lakes. Networks of tree roots help to keep soils in place, mimicking the porous earth of forests. Forested waterways are also better equipped to intercept sediment pollution, filter contaminants, and slow runoff that causes streambank erosion, all while providing favorable forage and habitat for birds, bats, insects, and aquatic life. Indeed, in the absence of riparian buffers, waterways become degraded. Impacts upstream quickly move downstream. Below are just a few of the ecological problems of exposed waterways:

  • Sedimentation: without vegetation to stop the runoff of solid particles and minerals, excess sediments enter the water and accumulate at the bottom, depleting aquatic oxygen levels and suffocating wildlife. 
  • Algal blooms: “nutrient pollution” from excess nitrogen and phosphorus leaching off croplands promotes a runaway “bloom” of algae on the water surface. This overabundance of algae depletes oxygen levels and blocks critical sunlight from reaching the stream floor. Nutrient leaching, especially of nitrogen, is a common side-effect of intensive agriculture that relies on industrial fertilizers. 
  • Streambank erosion: rapid runoff and unstable soils expedite the otherwise natural process of erosion along the stream edge, creating inhospitable conditions for fish and macroinvertebrates (aquatic insects) that depend on intact edges to spawn. This leads to population declines that can ripple up the food chain.
  • Temperature: without tree cover in the summer, unshaded waters overheat, making them uninhabitable for aquatic organisms. This is becoming increasingly common as our climate changes. 
  • Food availability: fish and aquatic insects require leaf litter that accumulates in the fall and winter to weather the cold seasons. Missing vegetation around the stream results in a lack of these vital nutrient sources, again destabilizing the base of the food chain. 
  • Carbon sequestration: trees and grasses are essential for balancing atmospheric carbon dioxide and absorbing the excess of greenhouse gasses emitted by human activities like the burning of fossil fuels. Simply put, missing vegetation is another missed opportunity to work proactively against climate change. 
  • Human value: Unstable streambanks, eroded soils, and a lack of biodiversity negatively affect our mental health and sense of belonging in the landscape.

While our regenerative farming approach does not apply chemical inputs like herbicides or synthetic fertilizers to the ground, we still see the impacts of a vacant landscape along our stream: drastic erosion, sediment deposits, and fast-moving water that, in 2021, partially flooded our riparian plantings.

Many locals will remember, as well, the destructive flash flooding of 2018 that affected much of York County, which was a major push for the Horn Farm Center’s turn to watershed health as an essential companion to healthy agriculture. Lastly, with runoff controlled by the return of a root web to the land, the farm will benefit from greater infiltration to better recharge our groundwater supply for community gardeners and other uses. Water security on the farm is becoming increasingly unpredictable as we endure drier, hotter summers each year. 

Ultimately, the newly planted 8 acre riparian buffer, which will grow to 10 acres this spring, will have an incredible impact on the farm and the ecosystem we’re a part of–from wildlife habitat to water security.

And like a drop of water in a stream, ecology ripples outwards. This is one of nature’s many teachings: how healthy elements positively affect relationships beyond the scope of what we can see. With this reality, our regenerative landscape is not just for us and our other-than-human neighbors, but for the health of waters, ecologies, and generations downstream.

Winter view of a Miyawaki mini-forest row adjacent to the stream edge (3/2023). The Miyawaki method for forest generation is another tactic we’re using beyond conventional tree spacing and tubing as we rewild the riparian area along our stream. An upcoming blog post will spotlight Miyawaki planting at the Horn Farm Center–stay tuned!

Click here to read For the Whole Stream Part 2: Downstream

Click here to read For the Whole Stream Part 3: Beyond the Stream


About the Author: Andrew Leahy

Growing up in the foothills of Ricketts Glen State Park, Andrew spent his early life in the embrace of Northeastern PA forests, sowing the seeds for his ongoing enchantment with the natural world and its stewardship. While studying English and Music Composition at Muhlenberg College, he gravitated toward nonprofit engagement as a work study student in the college’s Office of Community Engagement. Now, at the Horn Farm Center, Andrew manages social media, develops educational programs, coordinates volunteer events, and collaborates on marketing projects, large events, and organizational capacity-building. Through all of this, he is a dedicated student of the land, with a life’s mission of learning (and providing spaces for others to learn) about bioregional ecology, regenerative agriculture, permaculture, foraging, and locally-focused ways of living in reciprocal relationship with nature.