Headwaters throughout the United States constantly face many pressures that threaten their integrity. New housing developments, new roads, yards and agricultural systems all introduce different forms of contamination into freshwater systems. One prominent streamside pressure throughout the country is agricultural grazing. Roaming livestock feeds on, or grazes, vegetation in fields and streams. This process can lead to rapid declines in stream health if not properly managed.

In the United States, agriculture is a multi-billion-dollar industry that sees universal demand from consumers. This incredibly high demand directly leads to extensive changes to our watersheds to account for the presence of livestock.

To meet this demand, open space is converted into farmland suitable for species like cows to roam and consume vegetation on land or in water, if lakes or streams are present. This shift to intensive use from meadow or forest systems introduces stresses to the riparian areas and waters that did not exist before. After conversion, our waters may experience increased sediment deposition from nearby land, increased nutrient loads that come from improperly managed pastures, and streambank damage from increased use from livestock. These stresses and pollutants come from non-point sources, making it hard to pinpoint exactly where they originate. Finding a universal solution is even harder, as a system wide approach should be taken to ensure water quality is preserved. Recommendations to minimize damage exist, but sometimes they can fall short.

There are many solutions available for pasture and livestock owners that not only benefit the environment but can also benefit farmers by decreasing the amount of time and money invested. One of the simplest solutions is to ensure that pasture vegetation maintains a minimum height of 4 inches. When the vegetation is kept near this height, root systems are given the opportunity to grow deeper and hold soil and excess nutrients in place.

Rotational grazing is another solution available to farmers that benefits people, water, livestock, and birds alike when enough space is available. Rotational grazing requires pasture managers to divide their land into different sections, or paddocks. When land is divided, livestock is kept to graze in one section while the vegetation in other paddocks grows out. When growth is depleted in one section and lush in another means livestock can be moved based on plant growth ensuring food and ground cover is sufficient for both the animals and the environment. The ungrazed plant growth serves as an important habitat for ground nesting birds like meadowlarks and an important nutrient barrier for our waters.

When improper practices and bare minimum efforts are applied, sediment from cattle walking paths and fields can be washed into the waterways, potentially smothering algae, fish and aquatic insects that call these waters home. Additionally, if streams are small enough, grazing can occur directly in the streambed or on the riparian buffer that is directly protecting the stream. This can cause foliage to die back and expose the streambanks to new conditions where they can cause erosion downstream, impacting other landowners.

Dust is dangerous in the water, but so are fertilizers, pesticides and nutrients from livestock waste that can leach into waters when riparian areas are damaged in heavily grazed systems. Roots from trees and riparian vegetation hold these compounds in the soil column where they are essentially inert. Without sufficient buffers along waterways, widespread death of fish and other stream wildlife is bound to happen when algae growth can inhibit proper levels of vital chemicals like oxygen.

In areas where it is possible, adding fencing around streams to reduce the impact of grazing animals ensures riparian vegetation can grow and root systems can remain intact. Fencing in grazing heavy habitats can also increase activity of pollinators and birds by ensuring specific habitats and conditions needed to host these groups are present.

Grazing comes in many forms. Large swaths of land can be used by cattle ranchers for habitat and feed or smaller plots can be used. Regardless, unless proper measures are taken to ensure sediment loss and nutrient retention are kept at appropriate levels to maintain healthy waters, this non-point pollution source can impact millions of downstream neighbors when managed improperly.

By Zack Smith

Resources:

Agouridis, C. T., Workman, S. R., Warner, R. C., & Jennings, G. D. (2005). Livestock grazing

management impacts on stream water quality: a review 1. JAWRA Journal of the American Water Resources Association, 41(3), 591-606.

Cole, L. J., Brocklehurst, S., Robertson, D., Harrison, W., & McCracken, D. I. (2015). Riparian

buffer strips: Their role in the conservation of insect pollinators in intensive grassland systems. Agriculture, Ecosystems & Environment, 211, 207-220.

DeYoung, J., & Leep, R. (n.d.). Grazing Streamside Pastures.

https://forage.msu.edu/extension/grazing-streamside-pastures/.

Undersander, D., Albert, B., Cosgrove, D., Johnson, D., & Peterson, P. (2002). Pastures for Profit: A Guide to Rotational Grazing. National Resources Conservation Service: USDA. https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1097378.pdf.

Ecosystem engineers are species that change the habitats in which they live. In the Trust’s program area, one ecosystem engineer that many would first think of is a beaver. However, there is another ecosystem engineer in our waters that is changing the way our streams and rivers flow: the Caddisfly.

While small, these small insects are incredibly important in their systems. Caddisflies are sensitive to pollution and other environmental changes, and by assessing their presence, stream scientists are able to get a good understanding of a stream’s health. If caddisflies are present and disappear, that may indicate stream conditions have changed enough to a point where caddisflies cannot live there anymore. Alternatively, if caddisflies have not historically been in a stream and appear, that could point to positive changes in a stream’s quality.

Perhaps one of the most important steps to using caddisflies to assess stream quality is knowing how to identify them. With many different types of aquatic insects living in our streams, being able to distinguish a caddisfly from another species ensures that we can be fully sure that we understand the communities in our waters.

Caddisflies have life stages in both the water and on land, but for our purposes we’ll be focusing on the aquatic stage of their life when they are larvae. To identify if an insect is a caddisfly, first look at the shape of its body. These macroinvertebrates, or animals without backbones, have long bodies that are usually smaller than 45 millimeters or about the size of a paperclip. Their heads have hard skin compared to the rest of their bodies and no antennae. They have 3 pairs (or 6 total) legs extending from their middle body segment which is called the thorax. Their abdomen, which is the segment farthest from the head, will be soft and fleshy with branched gills. The most notable feature of many caddisflies is a case that they make out of aquatic debris like branches, rocks and dead plants.

Caddisflies are in the taxonomic order Trichoptera and are very closely related to butterflies and moths, and use silk to build their unique cases! Found on rocks, logs, and other objects on streambeds, some caddisflies use silk to spin nets to construct their homes.  When found in large numbers, their silk nets have been known to improve the stability of streambeds around the world. In multiple studies looking at caddisfly larvae’s impact on the stability of the stream bed (also called substrate) during floods, it was found that the presence of certain caddisflies can hold substrate in place in many floods. This is very important because as our waters face more intense flooding caused by climate change, habitat stability for aquatic species is put at risk. Net spinning caddisflies decrease the chances of streambed removal by increasing the stress or pressure needed to push the sand, pebbles, gravel and larger rocks downstream. A stable refuge from stormwater is created in the process, and other species like small fish, crayfish, other aquatic insects and vegetation are less likely to wash away when high velocity flood waters come through.

Though small, the abundance of caddisfly larvae in our headwaters is important because of their importance in identifying and maintaining a healthy stream habitat. When spinning nets, these larvae are inadvertently benefitting other organisms in their system and ensuring downstream species are not disturbed by excess inflow of sediments. Despite the caddisfly’s small size, the importance of this ecosystem engineer in our local watersheds is very large! While it may take thousands of caddisflies to make an impact, their presence is felt by many stream residents.

By Zack Smith

Resources:

Cardinale, B. J., Gelmann, E. R., & Palmer, M. A. (2004). Net spinning caddisflies as stream ecosystem engineers: the influence of Hydropsyche on benthic substrate stability. Functional Ecology, 18(3), 381-387.

Johnson, M. F., Reid, I., Rice, S. P., & Wood, P. J. (2009). Stabilization of fine gravels by net‐spinning caddisfly larvae. Earth Surface Processes and Landforms, 34(3), 413-423.

Voshell, J. R. (2003). A Guide to Common Freshwater Invertebrates of North America.    McDonald & Woodward Pub.