How the Construction Industry Affects the Quality of Land and Water Resources

 

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Construction projects can improve social welfare, well-being and quality of life. Sadly, however, construction is not an environmental-friendly process by nature. Construction activities irreversibly transform valuable lands such as farmland and forests into physical assets such as buildings, roads, dams or other civil infrastructure. Habitat loss, degradation, and fragmentation are some of the most direct impacts of such transformation. Replacing natural ecosystems with the built environment has several impacts on water resources and quality.

The purposes of this article are twofold. First, it attempts to articulate the current understanding of the relationship between land use for development and the quality of land and water resources. Secondly, it presents the means available to reduce the land-use impacts through improved technologies, design or modified practices.

Effects of Habitat Destruction

Habitat is the place where an organism lives and finds food, water, cover, and space to grow and reproduce. Each organism has evolved to be adapted to a particular kind of habitat. Habitat destruction is the most significant driver of ecosystem damage, biodiversity loss, and species extinction and comes about because of a variety of human activities.

Construction plays a substantial part in the loss or conversion of agricultural land, both by the extension of human settlements and by the increase in the quarrying and mining used to provide raw construction materials. Agricultural land is often lost through the activities of quarrying and mining for the raw materials used in construction; it is lost when agricultural land is converted to other uses, whether for urbanisation, for roadbuilding, dams or other civil engineering projects; and it may also be degraded as a result of the local pollution or waste generation associated with construction and building materials production.

Loss of natural areas affects all of the ecosystem services that they provide. However, not all natural areas are created equal, and the impacts of development depend heavily on what type of ecosystem the area supports. This article highlights two crucial kinds of ecosystems in Malaysia: forests and wetlands.

Forests are important ecosystems. Among the many ecosystem services, they help to regulate the global carbon cycle and hence the rate of global climate change and conserve our soil and water resources.

Construction similarly contributes to the loss of forests and wildlands by their conversion to other uses; it contributes to the loss of forests by the unsustainable use of forests for building timber, bamboo and other raw materials for construction; by the use of timber to provide energy for building materials production; and indirectly by the atmospheric and water pollution consequences of the construction and building materials production activities.

Habitat destruction and degradation contribute to the endangerment of species. This loss is critical because species diversity in an ecosystem is vital for survival. If one species disappears, another species can fill its niche if there is a large enough pool of candidates. Biodiversity is the term used to describe the biological diversity of genes, species, and ecosystems. The greater the biodiversity in an ecosystem, the more stable and resilient it will be.

According to data from the University of Maryland, released on Global Forest Watch (2020), the tropics lost 11.9 million hectares of tree cover in 2019. Nearly a third of that loss, 3.8 million hectares, occurred within humid tropical primary forests, areas of mature rainforest that are especially important for biodiversity and carbon storage. That is the equivalent of losing a football pitch of primary forest every 6 seconds for the entire year.

Malaysia had the world's highest rate of forest loss between 2000 and 2012, according to a new global forest map, developed in partnership with Google. Malaysia's total forest loss during the period amounted to 14.4% of its year 2000 forest cover. The loss translates to 47,278 square kilometres (18,244 square miles), an area larger than Denmark (Butler, 2013).

Besides logging purposes, another reason for Malaysia's forest loss is the fact that construction projects are still being built on dangerous slopes and in ecologically sensitive areas. Year in and year out, environmental disasters such as landslides occur in the country but the construction industry seems hard to learn from their mistakes. On 4 Dec 2018, on the front page of The Star newspaper, it said Malaysia is a country with the 10th highest number of landslides in the world. This is not due to natural factors alone. The main cause is man-made.

Besides forests, wetlands also perform invaluable ecological functions. The rate of organic matter production in wetlands is among the highest of any ecosystem. Covering 9% of the earth's surface, they have been vital for human survival since the dawn of man. They mitigate flooding and damage from erosion, wind, and waves; facilitate soil formation; provide rich feeding grounds and habitat for water life, waterfowl, mammals, and reptiles; help regulate atmospheric carbon dioxide and methane levels; help maintain the global nitrogen cycle; and improve water quality by removing excess nutrients and some chemical contaminants. Essentially, wetlands provide stability, filtration and renewal for many of the global environment's natural processes. These various ecosystem services cannot be easily replaced.

Malaysia has an extensive area of wetlands. The Malaysian Wetland Directory lists 105 wetland sites, including mangroves and mudflats, river systems and tropical peat swamp forests, but they are rapidly disappearing. According to research by the World Research Institute published in the Star in 2015, Malaysia lost 4.6% of its mangroves from 2001 to 2012, an area larger than the whole Federal Territory of Kuala Lumpur, pushing coastal species towards extinction and exposing people to rising sea levels. We lost mangrove forests due to aquaculture and reclamation projects (The Star, 14 March 2015).

Effects of Habitat Degradation

A significant amount of the development has occurred at relatively low densities, with residential buildings surrounded by driveways, sidewalks, patios, lawns, and other managed landscaping. Many of these suburban landscapes support wildlife that is rare in more urban areas. However, the widespread replacement of millions of acres of native vegetation with primarily non-native ornamental plants in managed landscapes is a growing problem for the organisms that depend on native plants for food, shelter, and places to rear their young.

The impact of a non-native species depends on its ecological context, and many non-native species provide essential environmental benefits. One fundamental role of plants in an ecosystem is to create food for herbivores that can transfer their stored energy to higher-level predators. However, homeowners and landscapers have often chosen non-native species for their resistance to insects. Most insect species lack the physiological and behavioural adaptations needed to use non-native plants for food. If ornamental plants cannot serve as food for the same number, and diversity of herbivores, the energy available for food webs decreases. 

Effects of Habitat Fragmentation

A great deal of habitat can be lost not through outright destruction but through a process known as habitat fragmentation. Fragmentation happens when a road or other human activity devices a large habit into two or more small patches. Fragmentation does not just make patches smaller; it changes their makeup.

Landscape modification, whether for agriculture or development, not only destroys native vegetation in the area modified but also harms what native vegetation remains because of nearby increased land-use intensity. Landscape modification and habitat fragmentation negatively affect virtually all taxonomic groups, including birds, mammals, reptiles, amphibians, invertebrates, and plants, and is a severe threat to global biodiversity.

The conditions at the edge of each patch are different from the conditions in the interior. This perimeter zone is subjected to edge effects, including increased heat, faster wind speeds, and dry soil. Fragments are vulnerable to invasion by exotic species. Some species are specialists and require interior habitat. Forest-interior bird and frog species and shade-tolerant forest plants, for example, disappear when patches become too small and are mostly edge.

Even though roads themselves take up little space, they split habitat areas into fragments, reducing interior habitat and multiplying edge effects. Dividing a large patch into two smaller patches increases the edge habitat and dramatically decreases the interior habitat. Creatures in the interior are closer to edges, and if the new patches are too small, many do not have enough core habitat to survive. Smaller populations in remnant fragments are more vulnerable to genetic drift and inbreeding depression, may not be large enough to survive normal fluctuations in population size and may go locally extinct. 

Roads are barriers to movement and are particularly potent forces of fragmentation and destruction. Animals have not evolved to understand objects moving at the kinds of speeds automobiles travel. Many animals are killed as they try to cross in search of food or water. Some animals cannot crossroads at all, resulting in their populations becoming divided; the subpopulations created may be too small to persist over time and may go locally extinct.

Corridors that connect patches can also be destroyed by land development. Many animals need to move freely across the landscape in search of water and food, which may be scattered. They may use corridors to move from one food source or nesting area to another, to find new territory, or to find mates. Many plants depend on animals to spread their seeds as the animals move around. When corridors are destroyed, patches become islands, species may be unable to find scarce resources or mates, and local populations may go extinct.

Degradation and Loss of Water Resources

Before our cities developed into thriving metropolises, this continent consisted of diverse habitats, including forests, riparian corridors, wetlands, etc. Streams and lakes conveyed rainwater. Wetlands lined the ocean edge and functioned as natural filtering systems and as buffers from major storms. Rainwater infiltrated into the soil, replenishing groundwater supplies and contributing to stream-base flow.

Replacing these natural ecosystems with buildings, roads, and other infrastructure has several impacts on water resources and quality. As urban areas throughout the country are developed, little by little, throughout this development, natural water systems were slowly shifted and rerouted to create developable land. 

Eventually, urban areas were covered by impervious surfaces such as buildings, streets, and parking lots, preventing rainfall infiltration. Wetlands were diked and filled for farmland and building sites. Streams were diverted or confined within levees to irrigate farms and eventually buried in pipes. The pipes carried stormwater runoff from urban neighbourhoods directly into streams or oceans. Instead of percolating into soils, stormwater runoff travelled over impervious surfaces, mobilised pollutants like oil and debris, and washed them into the sewer system and natural water bodies—streams, lakes, bays, and oceans. 

Impervious surfaces changed the time and intensity of stream flows during rain events, and a chain of unanticipated consequences was triggered. These consequences are related to stream hydrology, stream pollution and nutrient levels, and aquatic life. 

Effects on Stream Hydrology

When land is left undisturbed, the natural processes connecting water, soil, and living things work together in self-sustaining systems. Rainwater in such a system stays where it falls or moves slowly. Soil does not usually become completely saturated during a rainstorm, so only a small portion of the water runs off the surface. What little water does runoff usually flow at a slow, meandering pace, during which suspended sediments have time to settle out. 

This water has been cleansed of particulates before it finally reaches stream channels. Deep below the surface, water slowly accumulates into pools of groundwater. Between rainstorms and during dry seasons, this groundwater gradually seeps into streams and wetlands, maintaining a steady baseflow and providing water to invertebrates, fish, and other aquatic creatures.

When forests and grasslands are replaced by rooftops and roads, the water-retaining function of the soil is cut off, and the flow of water is radically changed. Development causes fundamental changes to the water (or hydrological) cycle, the water movement pattern on, above, and below the earth's surface through processes such as evaporation, precipitation and infiltration.

The first effects occur once vegetation is removed from the landscape. Removing vegetation decreases the amount of precipitation that returns to the atmosphere through evaporation from the earth's surface and transpiration from plant surfaces (together called evapotranspiration). In developed areas, not only is the amount of vegetation diminished, sometimes significantly or even entirely, but impervious surfaces such as pavements, roads and rooftops increase, and the amount of water that runs off the surface of the land increases.

Increased runoff, in turn, has several effects on the water cycle. First, it reduces the amount of water that recharges the underground water reservoir and moves through subsurface pathways. This groundwater largely sustains streams by slowly flowing over days or weeks, so their reduction can lead to soils being dried out during dry periods; hence, streams and wetlands are cut off from their supplies of water.

Second, increased runoff makes floods more frequent and severe during wet periods, as water that would normally soak into the ground near where it lands instead cannot infiltrate. Increased runoff is a problem of increased water quality and increased water speed as it flows. Water that before might have been held below ground in this reservoir to be released slowly over days or weeks now flows rapidly across the surface and arrives in streams, in short, concentrated bursts, a condition known as "flashy" flow. Floods downstream are bigger. Streambanks erode. Water quality declines. In Malaysia, flash floods in densely populated urban areas, such as those in Johor, Kuala Lumpur, Penang, and some parts of Selangor, are also becoming very common.

The combined effect of urban expansion and agricultural intensification has exceeded the land's capacity to absorb exceptional rainfall levels. At the same time, rainfall has become more intensive, concentrated and erratic due to global climate change. This negative interaction is highlighted by an increasing rate of severe flooding witnessed in India, Bangladesh, China, Vietnam, Pakistan and Indonesia (World Resources Institute, 2015).

Not only does the amount of runoff entering water bodies increase as impervious cover increases, but the temperature of the water also tends to increase as well. Many impervious surfaces are dark. They transfer the heat they have absorbed to the water that lands on or runs over them. Warmer water holds less oxygen. Fish struggle to breathe in warm, sluggish, low-oxygen water. Local extinctions follow.

Effects on Water Pollution, Nutrients and Aquatic Life

Most small natural streams have very low levels of toxic chemicals; relatively low levels of dissolved solids such as calcium, nitrate, phosphorous, iron, and sulphur; and relatively low levels of suspended solids such as silt, algae, and organic debris. Development increases their concentrations in water bodied through stormwater runoff. 

Water that runs off impervious surfaces, mostly paving, picks up pollutants including oil, antifreeze, and pesticides. The pollutants become concentrated without access to plants and soils that could remove suspended particles, break down petroleum, and sequester metals and pesticides. This contaminated water then moves into pipes with its pollutant load and empties into streams.

Typical pollutants found in stormwater include the following:

Sediment: From soil erosion on bare areas or unstabilised construction sites, or it may come from impervious surfaces in developed areas where soil particles are deposited by traffic and wind. All land areas will contribute some sediment, but unprotected or disturbed areas can contribute vast amounts of sediment from relatively small areas.

Organic matter: Refers to natural materials such as leaves, sticks, grass clippings, and animal waste and to human-made materials such as papers, garbage, and other trash that finds its way into stormwater runoff. Organic matter also includes dissolved substances from tree leaves, paper, or plastic wastes. These dissolved substances serve as food for bacteria and other organisms, which multiply and consume oxygen. If this consumption reduces the oxygen to very low levels, the water may become foul, producing strong odours, and the number and mixture of aquatic species will change.

Bacteria: Urban areas have large populations of pets, generate much garbage and other wastes and have a significant number of native animals such as pigeons, seagulls, squirrels, and mice, all of which contribute bacteria to stormwater runoff.

Heavy metals: These include copper, mercury, chromium and lead; iron, aluminium and manganese; baron, zinc and cadmium. Metals in stormwater come from automobile emissions, weathering paints, wood preservatives, motor oils, and industrial and commercial spills and releases. Zinc found in runoff comes from metal roofs and gutters. Metals in stormwater are toxic in many forms of life and, in extreme situations, can contaminate public water supplies. Since metals can accumulate in aquatic animals, toxic amounts can move up the food chain, eventually affecting humans who consume fish or shellfish with high levels of accumulated metals. 

Toxic and synthetic chemicals (pesticides): These come mainly from manufacturing products that have had chemicals leached from them, from industrial processes, and from fossil-fuel combustion and lubricating oils. Stormwater runoff may pick up pesticides used for controlling nuisance vegetation and animal pests. Many of the chemicals can accumulate in the food chain, possibly threatening aquatic life, fish, and food for humans.

Oil and grease: Oil and other lubricating agents leak from vehicles and are washed during rainstorms from roads, parking lots, and any areas of intense automobile use. Most of the oil and grease bunds to sediment, eventually settling to the bottom of water bodies. This oil and grease concentrate and can adversely affect the organisms that live in the bottom sediments.

Plant nutrients (fertiliser or phosphorous): Common plant nutrients include nitrogen and phosphorous compounds, which are chemicals found in commercial fertilisers and animal manures that promote and sustain desirable plant growth. However, when these same nutrients reach water bodies, they can cause undesirable growth of algae, bacteria, and plants, creating nuisance algae blooms and overgrowth of bacteria plants in the water. 

Since only small amounts of nutrients are required for the accelerated growth of algae and plants, controlling the amount of nutrients entering stormwater is very important to protect receiving waters. Nutrients enter stormwater from a variety of sources, including runoff from fertilised lawns and gardens, agricultural fields, leaks from sanitary sewers, and wastewater from septic tank systems. Intensely landscaped areas, such as golf courses and industrial and commercial parks, can contribute large amounts of nutrients to stormwater. 

Excess plant nutrients in water cause a process called eutrophication, which occurs as plant nutrients accumulate in a water body, causing increasingly heavier growths of plants and algae and reducing the amount of oxygen in the water available for fish and other animals. As eutrophication progresses, water bodies can experience algal scums and blooms, cloudy and discoloured water, strong odours, and fish kills. Although eutrophication occurs naturally at a slow rate, it is greatly accelerated by stormwater pollution.

How the Construction Activity Should Change

There are many ways in which the nature of current construction activity can be changed to make it less environmentally damaging, without reducing the useful output of construction. They can be divided into two categories: where we build and how we build.

Where we build involves locating development in a region or land area. It includes:

• Safeguarding sensitive areas such as riparian buffers, wetlands, prime agricultural land, and critical habitat from development pressures.
• Directing new development to infill, brownfield, and greyfield sites to take advantage of existing urban infrastructure and reserve green space.
• Reusing existing buildings, including interior and exterior materials, to reduce the energy use and environmental impacts associated with producing new building materials.
• Putting homes, workplaces and services close to each other in convenient, accessible locations.

How we build includes:

• Developing more compactly to preserve open spaces and water quality.
• Increasing the density of development or redevelopment to help minimise opening up new greenfield sites, preserve existing habitat and natural resources, and minimise the use of private modes of transportation.
• Mixing uses to reduce travel distances.
• Designing communities and streets to promote walking and biking.
• Protecting existing natural areas in site development and restoring damaged areas on already impacted sites to provide habitat and promote biodiversity.
• Implementing an erosion and sedimentation control plan for all construction activities to control soil erosion, waterway sedimentation and airborne dust generation.
• Increasing the use of wood products in the building from forests certified for sustainable harvesting and good management practices. 
• Increasing the use of mineral, agricultural and demolition wastes in construction. Not only would this reduce the impact of construction on the natural environment by reducing the need for quarrying, mining or logging, it would, at the same time, reduce the undesirable environmental impacts associated with the disposal of those mineral wastes. Among the more promising developments are natural fibres as reinforcement in concrete roofing; construction boards from organic wastes; secondary timber species utilisation; rice-husk ash cement, and asphaltic sheets for roofing.

The adverse effects of degradation and loss of water resources can be reversed through sustainable stormwater strategies that promote the use of ecological and natural systems for the management of stormwater quality and volume. The spatial planning system and the design of buildings and landscapes have a role to play in absorbing the stormwater runoff, thereby reducing stress on our engineered drainage systems and river systems.

All sustainable stormwater strategies are based on the same three fundamental principles: 

Think small: sustainable stormwater management focuses on small storms. Allowing water from the small, frequent rainfalls to infiltrate will restore most of the watershed's function. Small frequent rainfall amounts can be infiltrated on every site. With every site plan contributing to incremental changes, designers can work toward restoring natural hydrological function in the urban watersheds. While this is an enormous, long-term effort and managing runoff from a single development site may seem inconsequential, by changing the way most sites are developed, we will be able to protect water quality and preserve natural ecosystems in our urban and urbanising areas.

Start at the source: sustainable stormwater management retains the water where it falls instead of transporting it. Treating and infiltrating a small amount of water at a time, when repeated in multiple locations across the land and when repeated for every small storm and the beginning of every large storm, will restore water quality, most of a stream's baseflow and most of the groundwater level.

Minimise impervious surfaces: sustainable stormwater management is essential for removing pollutants from water.

Natural stormwater systems achieve multiple goals. They reduce runoff's velocity and peak volume, restoring stream baseflow, limiting erosion, and reducing flooding. They recharge aquifers. They remove or neutralise pollutants. They can lower costs by replacing much of the expensive stormwater infrastructure that would otherwise have been constructed. At the same time, they provide a habitat for native plants and animals and esthetically pleasant places for people. Many places designed to infiltrate and treat stormwater also function as landscape elements or as public open spaces for recreation during dry weather.

Urban stormwater runoff must be managed using best management practices to clean stormwater before it leaves the site or reduces or prevent pollution from entering lakes and streams. Low-impact development is a term that is sometimes used to describe the approaches to stormwater management that work with natural systems to manage stormwater close to its source. The best-known stormwater best management practices are low-impact development strategies and include rain gardens, vegetated swales, porous paving, green roofs, and constructed wetlands.

The balance between the natural environment and the man-made environment should be considered carefully in planning and design. Prediction of the environmental impacts of construction in the early stages of projects may lead to improvements in the environmental performance of construction projects and sites.