Investigating Biodiversity on Pennsylvania Dairy Farms

Alliance for the Chesapeake Bay Forests and Agriculture teams doing a survey of woody vegetation in a riparian forest buffer on a dairy farm.

Riparian forest buffers can benefit both the flora, the fauna, and the water quality in and around streams. In April of 2026, the Alliance started a biodiversity pilot study to understand the impacts of its previously planted forest buffers. Quantifying the biodiversity benefits of buffers on farms is the first step toward creating a biodiversity index that can be replicated and applied to many agricultural systems, transforming the industry’s ability to invest in biodiversity within the supply chain. The participating farms are Dairy Farmers of America (DFA) farmers that supply milk used in some ALDI products. This study is a partnership between the Alliance, DFA and their farmer-owners, and ALDI, who is the project funder.

What the streams can tell us

Aquatic invertebrates caught in one kick net sample from a Lancaster County stream.

The Alliance is conducting biodiversity surveys at three different types of farms:

• Farms with well-established forest buffers already in place (planted at least four years ago)
• Farms with newly-planted forest buffers set to be planted this fall
• And farms with no riparian forest with bare streamside areas

This pilot study will last for two years and include two types of biodiversity surveys. The first, held in April, focuses on the stream itself, including water quality and aquatic invertebrates, as well as surveying the woody vegetation present in the riparian zone. The second, held in May, focuses on the buffer zone by the stream, including surveying for birds, herbaceous vegetation, and invertebrates. This sampling has been completed for 2026 and will be repeated again in 2027.

Temperature and pH are important water quality indicators, when either of these parameters stray from the normal range, aquatic organisms can be severely affected.

The goal is to gather information from farm streams with a wide variety of riparian buffer statuses. Water quality can be measured in many ways. We focused on four core measurements: temperature, pH, nutrients (Nitrogen and Phosphorus), and aquatic invertebrates. These parameters tell us about the health of the stream–we can especially learn a lot about the pollution tolerance of the aquatic invertebrates present. All of the eight farms included in this study lie within the Chesapeake Bay Watershed, so protecting these local streams also has big impacts downstream.

What do we find on the land?

Waterfowl, like this Canadian Goose, play an important role in both terrestrial and aquatic environments.

Outside of the water, the Alliance is taking note of woody and herbaceous species, bird populations, and invertebrates. The vegetation lining these streams vary widely, some are densely wooded forests with planted native trees, others are predominantly pasture and consist mostly of herbaceous forage, and many fall in the middle of the spectrum. Riparian forest buffers can be teeming with songbirds in the morning, but we also monitor them at night, keeping an ear out for owls. There is a diverse world of invertebrates flying around our heads, crawling over leaves, and burrowing underground. In this study, we used nets to catch and identify terrestrial invertebrates, soil samples to see what is living below our feet, and UV lights to identify nocturnal invertebrates.

The goal is to see if there really is a difference in biodiversity between these types of farms, and the number and types of critters we find there. This data will give a great snapshot of the biodiversity of each farm, and at the end of the study we can quantify the impact that riparian forest buffers have on it.

Herbaceous vegetation surveying in a pasture finds a variety of grasses, legumes, and forbs.

The Alliance’s focus is on clean water the Bay as whole, but the Agriculture Team is also interested in regenerative agriculture to reduce greenhouse gas emissions, increase carbon sequestration, improve soil health, and enhance biodiversity. Perhaps most importantly, though, the Alliance aims to improve the long-term sustainability and profitability of the farms we work with.

While water quality and climate benefits of on-farm best management practices (BMPs) is well established, there is less data on biodiversity on farms. Biodiversity is more difficult to quantify, so the Alliance hopes to investigate these three types of farms and provide more insight into what our favorite critters indicate.

Thank you to DFA for partnering with the Alliance on this exciting endeavor, and to ALDI for funding our efforts. Stay tuned to see what we find out!

Learn more about the Alliance’s corporate partnerships