How do green spaces lower temperature in cities?

Green space or the open natural environments in the cities are the lungs of the cities. It can be in the form of  public parks or private campuses and community/institutional parks/gardens. State and national parks or open country spaces on the periphery are not urban green spaces as their benefits for the city are limited.

The benefits of urban green spaces are unlimited. Man's bond with nature is ancient. Nature is a source of inspiration and relaxation for humanity. People living in stressed, congested city environments often long for the countryside natural environment. The individuals and communities near green spaces receive valuable positive benefits, which may be in the form of pure air, better physical or mental health, recreation and much more. However, these benefits are not only limited for humans but the city environment also benefits from these green spaces.

Role of green spaces in reducing the temperature of the cities is widely accepted. Concrete city structures get heated up quickly during day time and release heat during night. Due to this, the average temperature in cities can be 1-3 degrees celsius higher than in the surrounding rural regions. This results in the formation of  Urban Heat Islands, or UHIs. If we try to visualize the temperature profile of urban and surrounding rural regions graphically and spatially, it will show an island of higher temperature than surroundings. Thus it is named as urban heat islands. The concrete structures in the cities are mainly responsible for the heat island effect. The pollution from the automobile and industry releases carbon dioxide. CO2 is a known greenhouse gas which increases temperature of the cities.

Green spaces within urban areas can restrict the direct heating of the concrete pavements. The tree canopy reduces the incoming solar radiation through shading.  The process of evapotranspiration reduces heat by releasing water into the air. Some factors like type of  green space (park or nature reserve), type of plant species, and the density of vegetation also plays an important role. For instance, trees with broad canopy like banyan or peepal trees, provide shade in a larger area and are more effective in reducing heat. Thus, green spaces decrease the overall effect of UHIs. The larger the green spaces in the city, the smaller will be the heated areas. Clustered green spaces are more effective in reducing temperature. Green spaces are also helpful in reducing pollution by absorbing carbon dioxide and releasing oxygen. This green space works in many ways in reducing the temperature of the cities.

The world of corals

The Great Barrier Reef is the largest coral reef system in the world visible from space.

Corals, the beautiful plantlike structures in the sea floor, are actually hundreds to thousands of tiny creatures called polyps. Soft polyp secretes a hard skeleton of limestone that attaches itself to other sea structures like rock or dead skeletons of other polyps. Polyps live in colonies and grow connected to each other. They are dependent on one another for survival.

 

Most coral reefs are found in the warm shallow waters of tropics and subtropics. About 90 percent of the world’s coral reefs occur in the Indo-West Pacific region. Some Reef systems also exist in the West and East Atlantic, and East Pacific oceans between 30° N and 30° S. Major Reef systems are recognised on the basis of their location like Caribbean reefs; the Great Barrier Reef; the Red Sea; Arabian Sea; and Persian Gulf reefs.

                                                     Distribution of the world's coral reefs                                    Cartographer: Hugo Ahlenius

 

Out of them, The Great Barrier Reef is the most well-known. It’s the largest coral reef system in the world, extending 2,300 kilometers from the Torres Strait, just south of Papua New Guinea down the eastern coast of Australia. It is the world’s largest structure built from living organisms visible from space.

Coral reefs are among the most complex and fascinating marine ecosystems in the seas and are home to the planet’s most diverse habitats. That's why they are sometimes known as the “rainforests of the sea.” Nearly a quarter of all the fish in the sea and many other organisms rely on healthy coral reefs. 

Coral reefs are known as the “rainforests of the sea.” as they are habitat for fishes and  many other organisms.

 

The Northwest Hawaiian Island coral reefs are home to about seven thousand species of plants and animals. They are not only home to many marine species, but they are a source of livelihood for many local communities. Millions of people around the world rely on fish caught in and around coral reefs. 

 

Corals are a source of livelihood for many local communities.

The reefs also draw in tourists, which helps the local economies. Coral reefs protect people and land from storms as well, serving as a barrier that reduces the impact of large waves on shore. 

However, they’re increasingly threatened from pollution, increasing ocean temperatures, overfishing, water pollution, coral bleaching and ocean acidification. Coral reef systems are most sensitive to pollution and increasing ocean temperatures and this can adversely affect humans and marine species alike. It results in coral bleaching where stressed corals expel their symbiotic algae causing them to turn white. The absence of the zooxanthellae in ocean waters causes the coral to have limited food supply and they become more susceptible to diseases.

Corals are under severe threat from pollution, increasing ocean temperatures, overfishing, water pollution, coral bleaching and ocean acidification.

 

Recent research shows that the world has already lost nearly 20 percent of its coral reefs and many more reefs are under severe threat. It is now needed that preventive and mitigating steps are taken to prevent further deterioration of coral reefs and their extinction.

Reference -

Distribution of the world's coral reefs, 2010, Cartographer: Hugo Ahlenius, Available at -https://www.grida.no/resources/7765

Images form Pixabay