by Mark von Wodtke, FASLA

An urban forest is a major community asset that lasts hundreds of years.  If well managed, it can provide the community with many valuable benefits that far exceed its cost. Like a natural forest, our urban forest needs to continuously regenerate to be sustainable. 

To realize the full potential of our urban forest, Claremont needs to develop a team that not only includes a certified arborist, but also an urban forester, as well as landscape architects and engineers who will carry out positive changes to enhance our green infrastructure.

Urban forests help rebalance the atmosphere by releasing oxygen and sequestering carbon to mitigate the effects of climate change. The urban forest is an extension of our lungs and also provides shelter to mitigate extreme weather, such as extended heat waves. There are many human health benefits. For example, Japanese studies have shown that immersion in a forest decreases stress and strengthens people’s immune systems. American and European studies have documented that people recover from illness faster if they can see vegetation. 

Here is some of what our community could do to improve Claremont’s green infrastructure:

We can add trees with more leaf surface near freeways to filter dust and particulates. This will also help mitigate freeway noise. Studies have shown that living close to freeway corridors affects lung development in children and also adversely affects mortality in the elderly, particularly those with cardiac conditions.

We could use tree inventory software to map the amount of leaf surface we have within 300 feet of freeways. Evaluating this, we could find places to add more trees, particularly species which are good filters. On this basis, we could implement enhancements of tree filters along freeways and along public streets and parks near freeways, as well as around schools. Funding for this may be available from Caltrans and the Air Quality Management District.

We can maximize the capacity of our green infrastructure to absorb greenhouse gases. Again, we could use tree inventory software to map the current amount of standing biomass. On this basis, we could determine ways to increase the capacity of our green infrastructure to assimilate greenhouse gases. Our green infrastructure team could select tree species which are particularly good at absorbing carbon dioxide and add more of these trees. They could sustain an active tree replacement program to regenerate the forest so that we always have a good number of these species growing in their prime. Funding for this could become available through emerging programs requiring that polluters pay for mitigating carbon emissions that are changing the climate.

We can shade even more street pavement and public parking lots with tree canopies to reduce the heat island effect. This also reduces evaporation of VOCs from pavements, minimizing air pollution, and saves money by protecting asphaltic pavement from the sun so that it does not need to be resurfaced as often. If done well, this program might pay for itself while enhancing the comfort of the community and reducing air-conditioning costs.

We can reduce pavement to provide more space for trees and allow runoff to percolate into planting areas for natural irrigation, filtration and reduction of storm runoff. We should transition to permeable pavers, which don’t off-gas chemicals that may cause cancer. We can install bio-filters to naturally clean up runoff from pavement. These positive changes to our green infrastructure will pay for themselves on the lifecycle basis, especially if we account for hidden costs to our health and the environment.

We can sequester the carbon produced by our urban forest. As long as trees are alive they embody a considerable amount of carbon which they assimilate from the air. If the city, and its maintenance contractors, would produce biochar from green waste and use it to condition soil, we could sequester carbon for centuries. Returning carbon to the soil improves retention of moisture and nutrients, making trees healthier. 

We can also salvage hardwood on a sustainable basis from the wide variety of trees in our urban forest. However, because our primary goal is to sustain our green infrastructure, we should only remove trees that are no longer a productive part of the urban forest. Craftsmen could use this salvaged wood to make collectable furniture and cabinets that would sequester carbon for hundreds of years.

Claremont could attract a team of capable professionals who will implement these and other policy recommendations to improve our green infrastructure. Claremont could share information to help the International Biochar Initiative address climate change. (Visit the website www.biochar-international.org for more information.) 

What we need is public support and the political will to invest in improving our green infrastructure for the health of our community.