Importance
of Trees in South Texas
By
J. Cantu
With a steady increase of
the world’s population now residing in cities, there is greater need to
understand how the complex interactions between the natural environment and
humans affect ecosystem services on multiple levels, especially for those that
are particularly important in the functioning and resilience of urban areas.
Ecosystem services, or the goods or benefits derived from nature, provide
mankind with most necessities of life and survival (Brown, Bergstrp et al.
2007, Wratten, Sandhu et al. 2013), and are often divided into separate
categories : supporting services (such as water and nutrient cycling),
provisioning services (i.e., production of food, fuel, and timber), regulating
services (such as rainwater retention, carbon sequestration), and cultural
services (aesthetic and spiritual values) (Sandhu and Wratten 2013). We know
nature provides a multitude of services to the community, yet a commonly
underappreciated function, is the growth of urban trees.
This
is a common sight when it rains in the valley. When looking at the street, many
buildings, streets, and sidewalks can be seen. These impervious surfaces
prevent water from draining and causes flooding. On the other hand, there is
only a handful of trees that can be seen. Trees function like
retention/detention structures (Nowak and Dwyer
2007), ultimately slowing down the rate of runoff. As the amount of
impervious surfaces increases with urbanization, it becomes increasingly
difficult to mitigate storm water runoff and cost-effective options become
limited (Barber, King et al. 2003). Due
to urban areas consisting of mostly impermeable structures, rainwater tends to
collect and cause flooding. When flooding can be attributed to inadequate city
drainage, this can be a result of poor urbanization practices (Pelling 2003).
Anyone who has lived in
the Rio Grande Valley, knows about the valley heat, especially in summer. Urban
trees cast shade and can shield from the wind, in which alters the neighboring
heat islands which can directly reduce solar heat gain through windows, walls,
and roofs (Akbari 2002). Trees also lower
surrounding air temperatures through evapotranspiration cooling, which can in
turn lead to cooler temperatures and less smog formation (McPherson, Nowak et al. 1997, Akbari 2002).
According to Dwyer, McPherson et al. (1992),
the annual space air-conditioning and heating cost for a home with efficiently
placed trees can be 4% lower, while a home with conflicting placed trees can cost
up to 9% more.
Trees
also help sequester a range of pollutants, even the pesky greenhouse gases. Trees
sequester carbon from the atmosphere during their growing phase. Although trees
are not the answer for reducing atmospheric carbon, they work as a short term
carbon sink as they grow (Jo and McPherson 1995). Airborne pollutants are also
a consequence of urbanization, and the removal of airborne particulates is a
health benefit that is of interest (Jim and Chen 2009). These airborne
chemicals can be sequestered as well by trees, allowing people to avoid harmful
pollutants. If urban forests can be promoted as means of mitigating pollution
within the scope of urban sustainability, then they can be used to improve
quality of life for people around the world (Escobedo, Kroeger et al. 2011).
In a study completed on the University of Texas- Pan
American campus, four regulating services (rainwater retention, electricity
savings by shade cast, pollution and carbon sequestration) were estimated and
valuated. As seen in the figure, the trees on campus provide services the
university. These trees have worth and these trees are not just bound by the
services described above. These few services only cover a fraction of what
trees can do for the community. These above services only slightly cover the
regulating services group. Trees also provide provisioning services (lumber and
fruits), cultural services (education and recreation), and supporting services
(habitat and biodiversity).
Trees should not be
considered only as money sinks, but should be seen more as assets. Trees
provide a plethora of services, and should be appreciated for it. With this
knowledge, the old proverb rings true, “The best time to plant a tree was 20
years ago, the next best time is today.”
