This is an important research question, I think, as the world becomes even more urbanized. Here’s a new study:

Vegetation Type and Age Matter: How to Optimize the Provision of Ecosystem Services in Urban Parks

As cities grow, urban greenspace assumes a more central role in the provision of ecosystem services (ESS). Many ecosystem services depend on the interactions of soil-plant systems, with the quantity and quality of services affected by plant type and age. The question, however, remains whether urban greenspace can be included in the same ecological framework as non-urban greenspace. Our previous studies have contributed towards filling this knowledge gap by investigating the effects of plant functional type (evergreen trees, deciduous trees and lawn) and plant age on soil characteristics and functionality in urban greenspace, offering also a comparison with non-urban greenspace. A total of 41 urban parks and five non-urban forest sites within and adjacent to the cities of Helsinki and Lahti (Finland) were included in this project. Path analyses presented in this contribution, combined with a synthesis of previous findings, offer strong evidence that urban greenspace functions similarly to non-urban greenspace. In particular, plant functional types lead to soil environmental modifications similar to those in non-urban ecosystems. Therefore, vegetation choice upon park construction/implementation can improve the quality and quantity of ESS provided by urban greenspace. However, although vegetation modifies urban greenspace soils with time in a fashion similar to non-urban greenspace, the vegetation type effect is greater in non-urban greenspaces. To conclude, our synthesis of previous studies provides science-based guidance for urban planners who aim to optimize ESS in urban greenspaces.

Urban Forestry and Urban Greening

Ecosystem services and ecological function are not exactly the same thing. Ecological function just is. Ecosystem services are what ecological functions do for people, and fit into the mainstream economic analysis framework. Part of the issue in studying this, I think, is scale. If you look only at one site, block, or park in a city, you might conclude that ecosystems services are negligible or un-measurable. If you look at the entire network and how it is connected, you might conclude that the effects are measurable and that there are policy and design choices that could make them better.

Biodiversity is something else again. More biodiversity is not always better, if it consists of more species of rats or coronaviruses, for example. But biodiversity may be a reasonable proxy measure for how the structure of a designed urban ecosystem translates to ecological function. This is useful if ecological function itself turns out to be difficult to measure. And I think the most useful measures might be biodiversity of animals such as insects (bees, butterflies) and birds. Because the plants in urban areas are mostly the ones that people put there. Biodiversity of plants can be improved through design choices, which is a good thing but in measuring that you are largely measuring inputs to the system rather than the resulting state of the system. Measure the animals, and you are measuring the resulting state of the system.

Measuring things that flit and flutter around might seem daunting. Well, you could try to do it with cameras and image processing of some sort. Or if you are interested in insects you can focus on larva, aka caterpillars. Tracking down bee and wasp nests seems a bit more risky, and you might also have a public relations problem trying to explain why more bee and wasp nests would be a good thing. But caterpillars don’t move fast, so trained people should be able to cordon off an area and find and identify them periodically. Let’s say you did this once a week for a year at several defined points in an urban area, especially if land use changes are occurring (or maybe some places they are occurring and some places they are not occurring.) Doing the same thing in nearby forests and/or farm fields might also add worthwhile data. Now you can do some data analysis and modeling, and maybe figure out design or policy choices that would help the little critters while also benefiting or at least not pissing off people or costing them any money. If you want to fund my half-baked research proposal, let me know.