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Bringing back our cities closer to nature
Humans have changed the face of the earth ever since people appeared on earth
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umans have changed the face of the earth ever since people appeared on earth. Even before the advent of agriculture, hunters and gatherers modified vegetation and forced some species of animals into extinction.
But the most drastic changes we have made in natural ecosystems have occurred over the last 150 years, and we are changing the face of the earth even faster.
With the increase in human population and the advance of technology, more areas are becoming urbanized. More people are living in cities.
In Asia, only about 20 percent of the population lived in cities in the 1960s, which rose to 33 percent in the 1990s.
It is predicted that by 2020, the percentage will be 50 percent. In developed countries such as the US, about 75 percent of its population currently lives in cities.
A city is a drastic transformation of a natural ecosystem. Most of its ecosystem has been eliminated, and consequently ecosystem functions have been crippled. An example is the disruption of material cycles in the cities.
In natural ecosystems, there is no waste. Buffalo dung, for example, serves as food for the dung beetle. Dead animals will be eaten by scavengers and subsequently decomposed by microbes.
Carbon dioxide from bush fires will be taken up by plants and changed into sugar through photosynthesis.
In cities, material cycles are broken. We produce waste and most of it is not recycled but becomes pollutants. There are two reasons why our waste does not go through natural cycles.
First, we produce too much waste. Jakarta produces 6,700 tons or almost 28 cubic meters of garbage each day. This amount of garbage at dump sites is too much and natural decomposition does not occur.
To make matters worse, garbage is also composed of non-biodegradable materials such as plastic, metal and glass.
Another example of the disruption to the natural cycle in cities is the water cycle. In natural terrestrial ecosystems, a great portion of rainwater goes into the soil, recharging groundwater, some of which is pumped again into the atmosphere by plants through transpiration, and some of which will flow into natural springs. A small portion of rainwater runs on the soil’s surface to wetlands and rivers.
In cities, most rainwater becomes run-off water because in most cities, land has been replaced by impervious concrete. As a result, after a brief periods of rain, the volume of water exceeds the capacity of cities’ sewers.
As wetlands have been drained and converted into housing or commercial areas, rainwater soon inundates low-lying areas of the cities.
The decrease of groundwater recharge coupled with the increase of groundwater exploitation in the cities also creates other problems, such as land subsidence and sea water intrusion.
Every year, the ground surface of Jakarta subsides several centimeters. This, of course, will exacerbate the flooding problem. Sea water intrusion into ground water also occurs in Jakarta.
The disruption of natural cycles in cities certainly causes environmental problems which in turn results in economic loss. The problems will get bigger as populations grow: More waste is produced, more buildings and roads are built and more wetlands are drained.
In natural ecosystems, material cycles provide free services of waste recycling and flood prevention. As cities depart further from natural ecosystems, we have to pay more for those services.
To reduce the cost of flood and waste problems, we must bring cities closer to natural ecosystems. To the maximum extent possible we must recycle waste material in cities. In natural ecosystems, waste from organisms is a resource for other organisms. In cities, waste from one industry can become a resource for others.
For example, waste from animal husbandry can be processed to produce methane which can be used as fuel. Sludge residue can be treated to remove pathogens and used as fertilizer.
Human excreta, as well, can be used as fertilizer if properly treated. Even sulphur dioxide, a toxic emission from coal-burning power plants, can be turned into calcium sulphate, the raw material to make wallboards for construction.
Plastic, glass and metal certainly can be reused and finally recycled. Many companies now design products that can be disassembled into reusable and recyclable parts.
When their products, e.g., photocopier machines and hand phones, are no longer used by consumers, those companies can buy back their products, disassemble the parts and remanufacture them. Several cities in developed countries, such as Canberra in Australia and Seattle in the US, have the great ambition to reach zero waste. One country, New Zealand, is also committed to reach zero waste by 2020.
For recycling programs to be successful, waste must first be sorted at the source. Simple as it may sound, sorting waste is difficult because we are not accustomed to this practice. Education is therefore essential. In comparison, Yokohama, Japan, gives it residents a 27-page booklet with detailed instructions on how to sort waste.
Our government must allocate funds to provide recycling in every neighborhood and to pay NGO facilitators who will help communities to manage the waste. Organic garbage can be easily made into compost for organic fertilizers and the community can hire a person to do this.
Other types of waste, such as glass, plastic and metals can be given or sold to scrap collectors who will then sell them to industries.
The water cycle should also be restored. Impervious parking spaces must be replaced with ones that allow water to percolate into soil. More land should be allocated for parks or open space.
As stipulated by the spatial planning act, at least 30 percent of the city’s areas must be designated as open green spaces. Trees in parks will reduce air pollution, especially dust and carbon dioxide, provide habitats for many birds and lower the air temperature. Trees planted around buildings also reduce the need for air conditioners.
Wetlands, such as swamps and mangroves, must be restored. Even, more wetlands need to be created. Buildings in low-lying areas should be relocated and the areas be made into wetlands which could serve many functions.
They will provide space for water to reside and give it more time to percolate into soil, recharging ground water, preventing land subsidence and reducing flood.
Wetlands also function as natural waste water treatment systems. They are also habitat for many aquatic animals and plants.
Natural ecosystems have many services to human. Bringing back cities closer to nature reduce environmental problems, making the cities more comfortable to live, and save us a lot of money which would otherwise be used to deal with problems such as waste accumulation and floods.
The writer is a lecturer at the University of Bengkulu’s School of Forestry and currently writing a book at James Cook University, in Queensland, Australia.
