For a newcomer to an area, a campus, or a neighborhood, for instance a tourist or an incoming student, few observations are more foreboding than litter. Not only does litter pose a direct health hazard, in that touching it can make you sick, it also implies the presence of people who don't care about this (and likely other health hazards), people who don't care about preserving natural beauty or civic pride, and people who don't respect the rights of the neighborhood and others to experience and enjoy it. While these impressions are obviously bad enough to motivate communities to prevent and remediate litter, they are still only conditional hazards. One could theoretically avoid physical contact with litter and litterers by going everywhere in their car, and eschewing outdoor activities in favor of a members-only gym. That's a primary conventional argument against investing in litter control--just avoid it. That argument might have been semi-logical in the past, when litter comprised mostly non-ecologically-active materials, but it doesn't hold up in the face of plastic.
Paper, glass, and metal are much less ecologically-active than plastic. Paper breaks down quickly and, critically, is digestible by most animals. Glass is essentially a rock, which most animals have evolved to avoid eating. Some metals are ecologically-active and harmful, but not the steel or aluminum used for food and beverage packaging. Metal cans usually have an epoxy liner, which is plastic but is shielded from the sun, so disintegrates slowly and is very thin compared to typical plastic containers. None of these materials, in the form of litter, pose a direct threat to animals and ecosystems like plastic does.
Plastic is different. Plastic is unique in that it disintegrates, into bite-sized microplastic, more slowly than paper but much faster than glass or metal. Plastic is unique because its size (especially after breaking-down), its color, its buoyancy, and its texture often mimic food. Animals of all sizes are now ingesting plastic and suffering or dying from it, especially in aquatic ecosystems, from whales and albatross swallowing entire large pieces, to turtles and fish, all the way down to plankton ingesting microplastic. Nearly worldwide, plastic-pollution is a threat to clean water and the food chain on which everyone relies.
So plastic has dramatically raised the stakes of litter and redefined the litter problem. Plastic pollution is doing the most damage now to aquatic ecosystems, largely because that's where a disproportionate amount of it ends up. Plastic tossed from a car might sit by the roadside for months or longer, slowly cracking, crumbling, or tearing into smaller bits, but most of it, even in a desert, if not picked-up, eventually gets washed or swept into a nearby creek, arroyo, or storm drain by heavy rainfall. Plastic pollution has made heavy rain and flooding in cities ecological disasters through the transport of unconscionable amounts of plastic into streams, rivers, and the ponds, lakes, wetlands, and oceans into which they flow.
While substantial plastic pollution comes from littered roads and city streets, an even larger proportion originates closer to the water. Litter associated with transient living now contributes a large fraction of the plastic load on our surface waters. The amount of plastic litter lining the banks of urban rivers worldwide associated with transient living is mind-blowing.
Transient living has always concentrated around rivers and streams, which provide fresh water for drinking, cooking, and washing. Before the rise of disposable plastic these human uses were largely tolerable by aquatic ecosystems, but not anymore. Plastic pollution has dramatically raised the stakes of homelessness as well. When rivers swell, which might happen only once every few years, entire tent compounds, with all of their trash, get washed downstream and pile-on the cumulative load of plastic in the lakes, wetlands, and oceans where the rivers discharge.
This is ugly but you must look. If we look and acknowledge these problems, as redefined by plastic, then something can be done about it, but our approach must be redefined too. Most governments are too compromised and unreliable. The volunteer approach is too sporadic, unspecialized, and critically fails to attach a cost to litter remediation. But there are enough people, regardless of socio-economic status, who still do care about public health, natural beauty, and civic pride, and recognize the threat of plastic pollution to them, that collective action in the private sector can contain it. It's just a man-made material. Are you out there?