Sustainable Solutions: Do Ferns Really Impact Urban Heat Islands?
By Rose Morrison, managing editor of Renovated
In the pursuit of sustainable living, ferns have emerged as a potential natural cooling solution in the face of accelerated global warming. These plants’ unique germination and reproduction traits make them well-suited to the rigors of growing in cities where the necessary resources for optimal growth — rich soil, water and adequate sunlight — are scarce. These conditions could make ferns another eco-friendly way to address the exacerbating effects of heat islands.
How Bad Is the Urban Heat Island (UHI) Effect?
Urban areas are characterized by concrete jungles, dense populations and industrial emissions. Together, these attributes create a heated, stifling living environment for residents. As a result, most U.S. cities are 10 degrees Fahrenheit hotter than their surrounding rural regions, higher during summer.
The UHI effect can lead to a cascade of issues, from higher indoor cooling costs and air pollution levels to increased heat-related illnesses and even mortality rates. With urbanization expected to climb in the coming years, these impacts could worsen and create inhospitable environments for future city dwellers.
Vegetal cover has been fundamental to counteracting the heat buildup in urban areas. Plants release moisture through evapotranspiration, which creates a cooling effect and helps reduce ambient temperatures. The more plants there are, the cooler the surrounding air and surfaces. Vegetation also acts as a natural filter, absorbing carbon dioxide and airborne pollutants contributing to UHIs.
The problem is these greeneries require ample land space to grow and flourish — a feature that is increasingly lacking in urban areas. Between housing, essential services and commercial requirements, the spaces available for trees and shrubs grow smaller.
The Role of Ferns as a Cooling Agent
A recent 2023 MIT publication has shed light on the possibility of using ferns to cool the planet. The study was prompted by recent findings in the Arctic Ocean, which suggested vast layers of Azolla ferns may have sequestered massive amounts of carbon and cooled the climate 53 million years ago.
These freshwater ferns, which were said to be up to 20 meters thick, formed a protective coating across the ocean, helping absorb much of the 50 degree Fahrenheit heat at the time. Researchers believe the region’s continental plate arrangements may have enabled a conducive condition for the ferns to thrive. As the plants died, the salty water preserved their organic composition, preventing the emissions of stored carbon.
Unique Properties
Among the countless vegetation species, ferns stand out for their unique characteristics that make them promising candidates for combating UHIs. These include:
- Reproduction: Ferns reproduce by spores, not seeds. The cycle begins with asexual spores contained in sporangia. Under the right conditions, these tiny cells get ejected into the air to land elsewhere and germinate. This process eliminates the need to prepare soil and plant seeds, which are difficult to accomplish in urban settings.
- High transpiration rates: Ferns thrive in high-humidity areas and exhibit high transpiration rates. During hot weather, some species can release large amounts of water vapor into the atmosphere, effectively lowering the temperature in the area.
- Low maintenance requirements: Ferns are known for their resilience and adaptability, requiring minimal maintenance compared to other vegetation types. They mostly flourish in temperate and tropical zones, similar to climate conditions in most urban heat island environments. Additionally, ferns are perennials, meaning they can live for several years unless inhibited by external forces.
- Adaptability: Ferns’ ability to tolerate fluctuating moisture levels and grow under diverse conditions enhances their potential for widespread implementation in urban environments.
Ferns as Part of Living Architecture
Ferns have been known to grow on rocks and cliffs, so the idea of using them as part of urban infrastructure may hold some merit. For one, they can be planted on rooftops or integrated into vertical green walls to create living systems that improve the building’s insulation and reduce energy consumption. Their dense foliage would absorb heat and protect surfaces from solar radiation.
Biophilic Design
Incorporating ferns into interior spaces like indoor gardens and atriums directly ties into the principles of biophilic design, which aim to blur the lines between residents and nature. Like most plants, indoor ferns can improve air quality and contribute to a sense of well-being among building occupants.
Stormwater Management
Climate change has increased the rates of erratic weather events, so cities generally see more intense storms and flooding. Urban spaces teeming with ferns can absorb excess runoff from paved surfaces and filter waterborne pollutants. These structures can help relieve the pressure on urban drainage systems and enhance sustainable water management practices.
Biodiversity Enhancement
Living architecture that includes native fern species can support a city’s biodiversity initiatives by providing habitat and food sources for various wildlife. This integration promotes ecological balance and strengthens urban ecosystems.
Combating UHI Effects Holistically
While ferns show much potential as a practical method for addressing UHI, they’re a long way from becoming an industry standard. Meanwhile, global warming rages on, and humanity must use every available solution to mitigate climbing heat waves and their associated effects. These measures include:
1. Energy-Efficient Cooling
Sustainable HVAC solutions are an excellent way for households and businesses to minimize emissions, which are among the biggest drivers of UHIs. For example, geothermal heat pumps draw on the Earth’s natural heat to regulate indoor temperatures, negating the need to burn fossil fuels. These systems can also reduce up to 70% of home heating costs while providing the same output as conventional HVACs.
2. Efficient Thermostat Management
Where investments in sustainable heating and cooling technologies are not yet viable, adjusting the thermostat to balance comfort and energy savings is the next best thing. According to reports, the optimal air conditioning temperatures are 78 degrees Fahrenheit when indoors and 85 degrees outdoors. Smart programmable thermostats make automating these settings according to residents’ schedules easy.
3. Cool Roofs
Cool roofs reflect up to 60% of sunlight, allowing the building to remain cooler than traditional materials during peak temperatures. They’re vital to addressing heat islands and are thankfully becoming a mainstay in modern city infrastructure.
Ferns Are a Promising Solution to Urban Heat Islands
Ferns can help regulate temperatures and humidity levels by creating microclimates around critical structures, reducing the heat island effect in urban areas. The presence of these resilient plants in strategic locations can cool the air, provide shade, and enhance thermal comfort for people and. buildings. It’s important to maintain a holistic approach to tackling UHIs by tapping into the more accessible resources while awaiting the fern revolution.
About the Author
Rose is the managing editor of Renovated and has been writing in the construction industry for over five years. She’s most passionate about sustainable building and incorporating similar resourceful methods into our world. For more from Rose, you can follow her on Twitter.