Landscape
Introduction
Lawns,
ornamental shrubs and trees, often poorly adapted to difficult urban
conditions, have for many years dominated urban landscape design. To
survive, these landscapes require high levels of maintenance, irrigation,
fertilizers, herbicides and pesticides. These not only increase the
cost of ownership, but pollute stormwater runoff and provide little
or no habitat for local wildlife.
Ecologically
based landscape design can change this pattern. It considers a region’s
water flows, climate, open spaces, native vegetation, wildlife and existing
urban development. Understanding the ecology of the region helps when
working with the needs of a specific site design, including its solar
access, wind patterns, topography, rainfall and drainage patterns, the
preservation of existing vegetation and unique features of the site.
In
recent years the City of Santa Monica has promoted a more environmentally
responsive approach to landscape design, particularly in water conservation.
Through the City requirement to use drought-resistant plants, restrict
the amount of lawn and the use of efficient irrigation systems, water
consumption has dropped significantly.
The
Required Practices focus on landscape design that conserves water and
improves water quality. Outdoor water use accounts for approximately
35% of overall water consumption in Greater Los Angeles, of which half
is used to irrigate gardens and landscaping. Planting drought-tolerant
vegetation, minimizing lawn areas and using drip irrigation can reduce
water use in the garden by 50% to 70% and overall water consumption
by 20% to 25%. By managing stormwater runoff through on-site surface
water retention and reducing the area of impermeable paving, fewer pollutants
enter Santa Monica Bay.
The
Recommended Practices address a broader range of environmental benefits
gained through landscape design. These include improving the microclimate
around buildings to reduce cooling energy consumption and improve occupant
comfort, reducing glare, enhancing the appeal of exterior spaces, providing
habitat for urban wildlife and creating opportunities for local food
production.
Controlling
Solar Gain and Improving Ventilation
Controlling
solar gain in a building through planting on south, southwest and southeast
sides of buildings is a very effective way to reduce cooling loads.
In Santa Monica, where southwest-oriented building facades have the
greatest solar heat gain, planting shade trees regulates heat gain and
reduces air-conditioning needs. Trees and other vegetation can also
shade paved areas and provide a canopy for pedestrians.
In
addition to controlling solar gain, landscaping and landscape structures
can enhance a building’s natural ventilation and cooling by influencing
wind flow. This requires the landscape design to respond to prevailing
wind patterns and local wind flow variations, and strategically locating
trees, hedges and shrubs to direct winds toward ventilation inlets and
create low-pressure areas at outlets. Dissipating turbulent, higher
velocity winds in circulation areas around buildings can also be achieved
by placing a multi-layered planting of large trees and shrubs with dense
foliage at the base and corners of buildings.
Air
Quality and Wildlife Habitat
Ecologically
based landscape design can improve local air quality by absorbing carbon
dioxide, producing oxygen and filtering particulates. Landscaped parks
and streets provide a “green lung” for the community. Building
roofs and balconies can be deliberately designed to accommodate vegetation.
Conventional roofs degrade air quality by replacing a site’s original
vegetative cover with an impervious surface that absorbs solar energy
and contributes to the urban heat island effect. Planted roofs provide
a living surface that cools and insulates the building, improves air
quality and protects roof membranes from ultraviolet breakdown.
Landscape
design can create important habitat for resident and migratory wildlife
by providing food and shelter. Through mulching and composting green
matter, ecologically-based landscaping can maintain and improve soil
fertility, retain soil moisture, stimulate soil-based microbial activity
and maintain the cycle of nutrients in the soil. In addition, the use
of native and other ecologically appropriate plants reduces water consumption,
maintenance requirements, and the use of pesticides and herbicides,
and increases the area's suitability for wildlife.
Health
Benefits of Ecological Landscaping
Finally,
environmentally based landscape design practices can have direct financial
and human health benefits. Capital and annual utility costs and regular
maintenance requirements can be reduced, resulting in lower overall
operating costs. Incorporating areas to grow food within developments
encourages local food production and reduces monthly food expenses.
It can provide occupants with a secure source of organically grown,
fresh produce. Opportunities to garden provide personal health benefits
that can improve the quality of life, particularly for older people
with leisure time to enjoy gardening.
