Professional Practice

15 of the 16 warmest years on record have occurred during this century, according to the National Oceanic and Atmospheric Administration (NOAA). 2015 also marks the 39^th consecutive year that the annual temperature has been above the 20^th century average. Rising temperatures intensify environmental threats, such as drought and rising sea levels. Higher average temperatures also lead to increased energy use and exacerbate pollution, which in turn raises health risks. According to the Intergovernmental Panel on Climate Change (IPCC), we are also seeing longer continuous stretches of higher temperatures that pose greater health risks than isolated hot days. Heat-related illnesses, such as heat stress, asthma, and malaria (mosquitos carrying the disease will travel further as temperatures rise) are expected to claim an additional 250,000 lives between 2030 and 2050, according to the World Health Organization. The effects of rising temperatures are pronounced in cities, where asphalt and concrete absorb and trap heat. This phenomena is known as the urban heat island effect.

How Resilient Planning and Design Helps

Trees are nature’s amazing cooling devices: they release water moisture, provide shade, and create micro-climates. Other designed green infrastructure -- green roofs, green streets, rain gardens, and parks -- can offer similar benefits. While a patchwork of trees, gardens, and green roofs cannot decrease temperatures, a system of them, combined with other tactics, such as the use of light-colored building materials, can be effective. Los Angeles is implementing this strategy with the intent of shaving 1.65 °C off of its city-wide temperature by 2035. Similarly, the cities of Melbourne and Adelaide heat reduction strategies include planting huge amounts of greenery; Adelaide, 100,000 square meters of it by 2020. The city of Stuttgart orients buildings to better leverage wind as a means of cooling their streets down. 

Co-benefits

Vegetation planted to cool down cities also helps manage stormwater, provide habitat for wildlife, and give streets character. Green roofs can provide many benefits – in addition to cooling the air, they can insulate the building, reduce building energy consumption, absorb stormwater, provide wildlife habitat, and create social space. Green infrastructure also creates lots of good local jobs installing and maintaining these systems.

Role of the Landscape Architect

Landscape architects play a lead role in greening our cities and communities in order to make them cooler. They work with architects and engineers to design green roofs, walls, and streets, and other green infrastructure as zones to inhabit during extreme heat events and hotter-than-average summers. Landscape architects can identify the tree and plant species best suited to generate a cooling effect while minimizing harmful volatile organic compounds (VOCs). Working with planners and arborists, they create urban forest plans and design and implement these systems.

ASLA 2010 General Design Honor Award, Rooftop Haven for Urban Agriculture, Chicago, IL, Hoerr Schaudt Landscape Architects

Relevant Projects  

ASLA 2010 General Design Honor Award, Rooftop Haven for Urban Agriculture, Chicago, IL, Hoerr Schaudt Landscape Architects

Stuttgart: Combating the Heat Island Effect and Poor Air Quality, Stuttgart Office for Urban Planning and Urban Renewal

Louisville: Cool 502, Louisville, KY

NYC Parks Green Roofs, NYC Parks Department and Columbia University  

Chicago Green Alleys, Chicago, IL

Melbourne Urban Forest Strategy, City of Melbourne

Resources

Estimated Biogenic VOC Emission Rates for Trees and Shrubs, U.S. Department of Agriculture 

Melbourne Tree Map, City of Melbourne

Research on Green Roof and Evapotranspiration, GritLab, University of Toronto  
 
Extreme Heat: Hot Cities—Adapting to a Hotter World, Symposium Report, Center for Architecture in New York, NY

Cool Pavement Guide, Landscape Architects Network

Heat Island Resource, EPA, Environmental Protection Agency

Urban Forest = Cleaner Cooler Air, ASLA

Tree Species Selection, Design, and Management to Improve Air Quality, University of Delaware

Urban Forests and Pollution, Extension

Quantifying Pollution Removal by Green Roofs, Science Direct

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