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Shining a Light on a Different Type of Stream Pollution

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Lights are everywhere around us and have many uses, often at night, that benefit our health and safety. We put lights on our cars, buildings, and roads, often neglecting to understand their full effect beyond their positive impact on human life. While lights may make us feel more comfortable in our surroundings, they have been known to negatively impact other species in our environment through the process of light pollution. 

Light pollution occurs when the excessive use of light creates an overwhelming glow in the night sky that brightens the natural environment, often exceeding even the bright glow of a full moon. This form of pollution is all encompassing, as 83% of the world population lives in an area that experiences light pollution. In the USA and Europe, 99% of the population lives under a polluted night sky. If you are interested in seeing what light pollution looks like in your hometown, check out this website. 

This image from https://www.darksky.org/light-pollution/ shows the potential pollution caused by lights in residential areas. All lights are used to light a specified area, but as seen in the image above, more areas outside of the area to be lit also experience glare.

Researchers have observed nocturnal animals that rely on dark skies and lunar cycles will change their activity levels in areas with more light pollution. Animal behavior has adapted to natural conditions over millions of years, and when we suddenly put in millions of lights, we are changing the environment species need to thrive. Perhaps the most common example of this is the case of the sea turtle. Hatching sea turtles rely heavily on the moon to find the ocean shortly after emerging. In highly polluted areas, the lights from the land often mimic or overpower the moon and deceive the babies, leading them towards land where they are bound to get hit by cars, eaten by predators, or starve to death (Longcore & Rich, 2004). 

Locally, different species feel the burden of light pollution. Studies on streams across the USA have shown that light pollution near streams can change the makeup of insect populations in and around streams. Streamside studies where artificial light pollution was introduced demonstrated that important spiders often living in riparian zones decreased in abundance, as did the diversity of aquatic insects, by as much as 16%. Light pollution near streams also led to a decrease in size in emerging insects by approximately 76% (Meyer & Sullivan, 2013).  

Changing conditions in streams can have a large ripple effect outside of the water, too. With individuals disappearing and shrinking in size, predators, like fish and birds, may have to consume larger quantities of smaller insects to meet their energy needs. Consuming more small insects can strain predators as they use additional energy to look for larger numbers of smaller prey. Less optimal food for these species can lead to decreased survival, further contorting the food web. 

In addition to changes within the stream corridor, light pollution brings many pressures to terrestrial insect communities. Bright lights are known to attract flying insects outside of streams – think of your porch light and all the insects that fly near it at night. This attracts more predators, such as bats, that feed on vulnerable species of insects near these lights. While some predators suffer because of light pollution, species like bats can benefit based on different behaviors in different areas. 

The map above shows the light pollution levels in Southeast PA. Philadelphia, a major city center, has incredibly high levels of light. Locally, West Chester, Marple, and Media all exert high levels of light pollution, as compared with the Trust’s program area, which experiences lower levels of light pollution thanks to lower development levels. These lower light levels can be attributed to protected lands. 

While avoiding light pollution is incredibly unlikely, there are solutions and actions we can take to minimize its effect on wildlife globally. At home, turning off bright outdoor lights or getting an automatic light can decrease light output. When choosing lights, picking lights that effectively target an area to be lit is important, as ineffective lights can cast a glow beyond the anticipated area and pollute more space than necessary. Within our communities, we can advocate for darker nights by telling our towns and cities to turn off unnecessary public lighting on buildings and in public spaces, much like Philadelphia did this last spring. As for protecting our waterways, planting and maintaining a healthy riparian buffer can go a long way in shielding waters from harmful light pollution. Thick plant growth will block incoming light and help keep our streams at lower light levels, ensuring aquatic insects, fish, and other riparian organisms can thrive. 

Citations:

Light pollution effects on wildlife and ecosystems. International Dark-Sky Association. (2016, September 12). https://www.darksky.org/light-pollution/wildlife/. 

Longcore, T., & Rich, C. (2004). Ecological light pollution. Frontiers in Ecology and the Environment, 2(4), 191-198.

Meyer, L. A., & Sullivan, S. M. P. (2013). Bright lights, big city: influences of ecological light pollution on reciprocal stream–riparian invertebrate fluxes. Ecological applications, 23(6), 1322-1330.

Header Image Eco Watch

Microplastic Pollution is No Small Problem

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By Zack Smith

Mankind’s mass production and consumption of plastic has reached all corners of our globe, from the depths of the oceans to the air around us. Plastic pollution comes in all shapes and sizes. Whether it is large chunks of styrofoam littering the side of the road or small fragments of broken down water bottles in our waters, plastic is constantly reaching new areas on our planet. 

One form of plastic pollution that has been getting increasing attention in the recent decades is microplastic pollution. Microplastics are pieces of plastic that are less than 5 millimeters in diameter. Surprisingly, some microplastics are produced at this size. These are called primary microplastics. Secondary microplastics occur when litter or other plastic refuse enters the environment and begins breaking into thousands of little pieces. The small size and widespread abundance of microplastics make them easily transportable in our world. Consequently, scientists have been finding plastics in almost every single spot they look for them — down to the organs of living beings. 

5 different types of microplastics seen in our headwaters.

While only discovered in our global waters and environments recently, microplastic pollution has been found in museum collection specimens dating back to the 1950s. This indicates that microplastics are persistent and likely have been causing harm to life on Earth for much longer than we realized. Plastics carry contaminants and pathogens and can cause harm to species by hindering their ability to properly function. Oceans, the atmosphere, and urban rivers have been the main focus of most microplastic research as they tend to accumulate in these environments because other outputs are constantly bringing microplastics to them. Despite being a global problem, very little has been done to document microplastic pollution in low order streams like the headwaters located  here in the Trust’s program area.

Over the past year, the Watershed Protection Team has been collecting and analyzing samples of stream water for microplastics to quantify the extent of any microplastic pollution in our area. Much to our surprise, microplastics are present in all of our headwaters at higher levels than anticipated. Dating back to March 2019, over 4,600 microplastics have been identified in roughly 200 liters of sample water.

Collection of microplastic sample using a glass jar

In 2021, our Watershed Protection Team has adjusted their sampling protocols to see how a plastic-free sampling method impacts the count. Before the Covid-19 pandemic, samples were collected using our typical monthly water sampling methods, which included storing water in plastic containers, using distilled water from plastic jugs, and storing dried samples in plastic bins. Clearly, when trying to quantify and describe a major pollutant you want that pollutant absent from all aspects of collection  — hence our new, plastic-free collection. The changes that we have made to our monitoring protocol have reduced the amount of plastic present in samples; we have yet to collect any field sample that is completely plastic free, which suggests that there is plastic in our waterways. 

A collection site at Kirkwood Preserve. Photo by Anna Willig

The hope is that this method will show truer values of the microplastics in our waterways and help us determine ways we may be able to further understand this pollutant. Our aim is to constantly monitor the health of our waterways so we can relieve any unwanted strain on our downstream neighbors. With microplastics present here in our headwaters, working to reduce their impact in rivers, bays, and oceans through small changes and constant monitoring at the source can go a long way.