Picture a vacant lot. If nothing comes to mind, the one in the photo will do. What would you find there? Litter, probably. Rats, perhaps. Maybe an old tire or two. Your first answer is probably not “climate change mitigation” or “better mental health.” But expectations aside, you could be getting both from that vacant lot and other accidental urban natural areas.
Weeds fight climate change? Well, yes, but not weeds especially – plants do. The list of ways urban trees mitigate climate change impacts is impressive, but they boil down to this: cleaner air, cleaner water and less flooding, cooler local temperatures, and better livability in the city generally. Trees aren’t weeds (except when they are), but any plant growing on that vacant lot shares some of the salient characteristics. They all photosynthesize. They all raise the relative humidity around them. They all sequester carbon within their structures. They all allow more rainwater to soak into the often-compacted urban soil. At core, “weeds” vs. “trees” is a distinction of human perception, and these climate benefits depend on what plants do and how they interact with the physical world, not how or whether we see those plants. True, some of the benefits of urban trees depend on the larger overall size of the trees to cast shade, but then again, some weedy species, like tree of heaven (Ailanthus altissima) or buckthorn (Rhamnus spp.), can get pretty big. Bottom line: look at that vacant lot again, and take a deep breath.
While you breathe, relax, because that same urban wild is also benefiting your mental health. Again, the list of mental health benefits from urban trees is lengthy, and again, it’s mostly about trees. In summary, humans evolved in natural environments, and therefore, we do better in some important ways when we can see natural environments. We think better, we feel better, and we treat each other better. Research on these effects usually shows a small benefit, but a (statistically) significant one, and these are easy benefits to get, with little downside. The research on benefits to mental health falls into three categories: benefits related to getting more exercise, benefits related to better social cohesion, and benefits related to stress reduction. Do you get these benefits from weeds as well as from trees? Yes, at least some of the time, but what matters here is how we see the weeds. Is that vacant lot a danger or an oasis? Are those weeds wildflowers or a home for vermin? Is that a deer or an assailant hiding in the underbrush?
That ambiguity makes it essential that we know whose health we’re trying to improve with these urban wilds and their benefits. Who you are makes a difference in how you see a given wild, and who you are also often makes a difference in where you live within a particular city. The demographic group, particularly race/ethnicity and gender, of the viewer can make a difference in how s/he views unmaintained vegetation, particularly whether it is threatening or desirable. The level of environmental education a person has, as well as how urban or rural a place s/he grew up in, can also matter.
More useful than sweeping statements about perception and demographic groups: it matters where you are in proximity to the wild area in question. You might enjoy the view from your 10th floor office while I worry about the overgrown lot across the street, but we could be looking at the same vegetated land. Each health benefit of urban wilds has its own geography. Some benefits, like heat island reduction, are best experienced by those closest to the wild site. Some costs, like depression of property values, are, too. Other benefits, like vegetated views and downstream reduction in flooding, may be gained by people too far away from the wild site to be affected by nearby burdens like increased pollen count or disease-carrying ticks. The same urban wild can simultaneously provide benefits to some and burdens to others, or some benefits and burdens to the same people at the same time. It’s not simply good or bad. It’s…both.
The question that matters, then, is how to manage wilds in your city for the most benefit and least burden to those most in need. What parcels are more valuable as wilds than as redevelopment, and why? What neighborhoods have the greatest health needs and the fewest resources with which to meet them? For parcels that remain wild, how best can they be managed to be healthy for nearby residents and positively viewed by the general public?
Climate change and healthcare share an urgent need for on-the-ground action that transcends contentious debate. Both are complex problems poorly suited to soundbite solutions. Both are negatively affecting the health of countless people, right now, today. If you had something that could make a difference in both areas without the need for political will or legislative action, wouldn’t you use it, even if the difference it made was small? Look out your window. That small difference may be closer than you think.