adminSydney Kawadza Senior Features Writer
Build a house and all your problems will wash away. True or false, housing provision has become a major priority for individuals, corporates and central Government. Unfortunately, urbanisation and development have had an adverse effect on the environment. Construction projects have encroached onto reserved and protected land. Authorities have had headaches with the haphazard establishment of residential areas.
The biggest impact of urban and industrial development has been on wetlands, leading to water shortages, environmental degradation and pollution.
Environmentalist Lewis M Cowardin describes wetlands as land where saturation with water is the dominant factor determining the nature of soil development and the types of plant and animal communities living in the soil and on its surface.
Wetlands vary widely because of regional and local differences in soils, topography, climate, hydrology, water chemistry, vegetation, and other factors, including human disturbance.
Environmentalists and urban planning experts, however, argue that the challenge is not insurmountable.
With proper planning, they argue, wetlands can be conserved.
Speaking to The Herald, Professor Danny Simatele of the Department of Geography and Environmental Studies at Wits University said the problem had become global.
Prof Simatele argues that Africa must wake up to the threat against wetlands.
“Urban space is diminishing in Africa and the only land available is on wetlands and with the development of technology, authorities have been forced to drain this land for development projects,” he said.
This, however, has had massive negative impact on the value and functions of wetlands.
“Wetlands provide a habitat for different species and have become the last reserve for migratory birds.
“When we drain these wetlands for construction purposes, the natural habitat is destroyed.”
Wetlands, he said, act as a natural filter for water purification.
He also added that at least 95 percent of water drawn from the ground is from wetlands.
Professor Simatele says the destruction of wetlands has led to increased pollution for urban water sources.
“Harare water once required few chemicals. However, because most of the natural water purification done by wetlands has been destroyed, the water now has high level of metals.”
He said councils had to put more resources into water purification.
Prof Simatele said wetlands controlled flooding in urban areas as they reduced run-off.
“Harare, Maputo or Lusaka, are experiencing increased flooding during the rainy season because we have destroyed the wetlands, which act as a natural sponge to absorb the water.
“Water is running freely on to our roads and houses while we are regularly experiencing flash floods in the cities.”
Professor Simatele added that wetlands were natural storage water tanks.
“However, we are shooting bullets into these water tanks, hence the water crisis in our major urban centres.
“Wetlands also act as natural carbon sinks because 85 percent of the carbon emitted into the atmosphere is extracted from the air by wetlands.”
He said destroying wetlands contributes to the carbon footprint causing climate change, drought and even flooding.
Professor Simatele dismissed the argument that appropriate technology while building can improve the wetlands system.
“That is totally false. We believe we can change the ecosystem for the better and that is wrong. We are where we suffering because of technology.
“Once you disturb the natural conditions of our environment they are lost forever. It is better to leave the environment in its state.”
Construction of such shopping malls as Zimbabwe Mall and Long Chen in Zimbabwe has led to an uproar among environmentalists, urban planners and local authorities.
“There is always an argument because property developers come with 3D presentations of shopping malls and offices that promise to create thousands of jobs and increased revenue.
“That is the understanding from our leadership who can quantify the benefits of such projects but are we able to quantify the benefits that we can derive from the wetlands like what the developer does?”
Zimbabwe Institute of Regional and Urban Planners president Mr Percy Toriro argued that development on wetlands should be done in a sustainable manner.
“This means that there must be a careful balance in which ecological considerations are also given importance.
“Unfortunately, of late we have seen many developments on wetlands. By far the biggest culprits are illegal land developers, also known as land barons.
“These have allocated and developed land in areas around Seke, Chitungwiza, inside Harare and other areas,” he said.
Mr Toriro called for consultations between town planners and environmentalists to arrest this unsustainable development practice.
“All development must be subjected to a sustainability test through environmental impact assessments. Where environment impact assessments are done, the negative impacts of development are minimised while mitigation measures are proposed.
“If these are implemented, logic will prevail and fragile areas are avoided.”
Urban development expert Mr Shingai Kawadza said building on wetlands affected human beings, their buildings and threatened the natural habitat for animal and aqua species.
He said this resulted in the extinction of rare and endemic species.
“Building on wetlands threatens the ecosystem dynamics. Introduction of impervious surfaces through construction of houses and other developments reduce percolation rates and ultimately the wetland ecosystem functions of acting as sponges which trap water or gradually release water to feed water systems are impaired resulting in reduced water to rivers and ultimately dams.
“It also changes habitats for wetlands animals and plants which may result in reduced aesthetics and loss of biodiversity,” he said.
Mr Kawadza said construction on wetlands should be avoided at all costs.
“Wetland constructions are always tricky — whether for housing or any other structures. Constructing houses on wetlands can be allowed as long as the densities are such that they do not impair wetland functions. They also have to conform to safety and health regulations.”
He attributed construction on wetlands to poor environment assessment, ignorance, maximising of profits and biased valuation of the environment where construction is earmarked.
He argued that authorities can control densities of development on wetlands and adopt better techniques in both construction and materials.
“Developments should be of low density and leave a lot of open spaces to ensure that wetlands functions in terms of regulating water percolation or infiltration are not impaired.
“Construction techniques involve using stilts and piles so that the buildings are not directly resting on the ground and water can still percolate.
“Techniques can also allow the use of grates along roads which allow percolation. The need for good drainage which channels water into open spaces or streams is also crucial.
“Use of light construction materials means that the ground is not seriously compacted,” he said.
Mr Kawadza also noted that urbanization has changes to wetlands functions as an ecosystem.
“As long as the changes are not huge, are spatial and temporary, construction can go ahead. If they result in serious alterations to ecosystems, then they should be modified.
“Safety for people involves ensuring the use of the right type of foundations which reduce cracking and also reducing the creeping of water up walls through use of sealants in the slab.
“Flooding can result from the introduction of impervious layers. This is why density of development on wetlands is important.
“Construction projects on wetlands will result in erosion of species, habitat fragmentation and purification of water is also affected, hence polluted materials are deposited in water bodies.”
Mr Kawadza observed that wetlands were in use in other parts of the world.
He said proper designs and construction techniques adopted could conserve wetlands.
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