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Trees: A Neglected, but Essential Component of Municipal Infrastructure

Nearly 6,000 years ago, in what is now Iraq, the Mesopotamians took an important step that would forever change the world: They turned the region’s well-worn footpaths, born of countless generations’ foot traffic, into the first stone-paved roads. In doing so, they enabled goods and services to flow easily through the region, and the civilization prospered. Many years later, humans civilization is utterly dependent on these and similar resources.

Today, we call these types of common goods “infrastructure.” Other examples include canals, reservoirs, dams, bridges, and tunnels. They are those things that make life easier for all citizens, and are often provided and maintained by local municipalities.

Gray vs. Green

Infrastructural assets are often divided into two different classes. “Gray” infrastructure includes those things made from concrete, plastic or steel, such as buildings and transportation routes. On the other hand, “green” infrastructure refers to living entities, such as rain gardens and street trees.

While the two classes have obvious dissimilarities, they provide similar infrastructural value, often at a lower cost to the taxpayer. For example, most major municipalities must implement and maintain a system for dealing with storm water runoff – a task that can be accomplished with gray assets (for example, a sewer system), green assets (such as rain gardens, street trees or wetlands) or – as common sense dictates – a combination of both gray and green solutions.

The Advantages of Incorporating Green Infrastructure

While civilization is unlikely to ever jettison sewers, bridges and dams completely, street trees, wetlands and other green infrastructure projects offer numerous benefits that traditional strategies do not. For example, trees and plants improve the quality of the air and reduce local temperatures through the process of transpiration. Virtually any tree installation will help reduce the area’s runoff water, but projects specifically designed to divert, absorb or store water – such as rain gardens – are especially helpful in this regard.

Additionally, while roads, dams and bridges usually fail to improve the aesthetics of an area, living plants and trees almost invariably make an area more beautiful. This increased aesthetic appeal translates to greater demand for local properties, which increases home values.

Empirical Evidence

It is important that green infrastructure projects are elegantly planned and suitably maintained. One challenge to implementing natural solutions is the perception that trees are an expensive and damaging resource, which will cause municipalities to pay more than they will save.

According to a recent study, nothing could be further from the truth.

Conducted by the American Society of Landscape Architects, American Rivers, the Water Environment Federation and ECONorthwest, the study examined almost 500 different green infrastructure projects in the United States. The researchers concluded that the majority of the projects (75 percent) cost the same or less to implement and maintain as similar, gray infrastructure projects did.

The study’s authors also determined that green infrastructure projects help cities use less energy and promote greater health among their citizens. This occurs as trees and their roots help filter bacteria and other pollutants from local waterways.

Additionally, many city managers and strategic planners worry that trees and plants will damage hardscapes, through the destructive action of their roots. However, as explained in a 1998 paper by Professor Kim D. Coder of the Warnell School of Forestry Resources, many problems blamed on trees are more appropriately placed at the feet of flawed hardscape designs.

From the study:

“Many infrastructures that concentrate and transport required resources for people are poorly designed and built to withstand natural processes over time. These engineering flaws are exacerbated by opportunistic tree roots colonizing new resource spaces.”

Simply put, better designed sidewalks and subterranean features will result in less damage from tree roots.

The Takeaway

The bottom line is that distinguishing between gray and green infrastructure is not always helpful – they both provide value for citizens and require resources to maintain. Moving forward, stakeholders must consider the empirical evidence and proceed deliberately, carefully considering all available strategies for coping with municipal challenges. Some solutions are better met with the help of trees, while others are more appropriately addressed through the construction of traditional infrastructural components.