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close this bookBasic Concepts in Environment, Agriculture and Natural Resources Management: An Information Kit (IIRR, 1993, 151 p.)
close this folderEcological basics
View the documentEcosystem degradation
View the documentHabitat and niche
View the documentThe food chain
View the documentBiological magnification
View the documentNitrogen cycle
View the documentSociety and the carbon-oxygen cycle
View the documentHealth consequences of environmental degradation
View the documentPopulation and the environment

Ecosystem degradation

Wheel of interacting forces affecting any ecosystem

The above is an illustration of the different factors involved in ecosystems degradation. The biggest responsibility involves the policy planners and implementors at the national, regional, provincial and municipal levels. The community (townsfolks, students, public officials, media and private entities) should play an important roles in the local use of the resources within each ecosystem. The role each one should play could be policing, reporting, organizing and taking hands-on-action to abate further loss of a tree, orchid, medicinal plants, bird and other animal species in an ecosystem. All of these are part of our national heritage. The conservation of which can be as joyful as the successful captive breeding of the Philippine Eagle or as sad as the plight of the Tamaraw. Much of the future of Philippine ecosystems depends on how we develop the social system which affects the ecological system.

If left alone and not irreversibly damaged, an ecosystem has the capacity to regenerate itself.

Impact of human activities on different ecosystems




1. Forest Ecosystem 6.7 million ha

Clear-cut logging

Continuous loss of forest cover


Rate of extraction at 100,000 ha/yr

Slash-and-burn activities

Loss of soil nutrient

Forest slopes soil exposed to onslaught of varying climatic conditions

Forest harvesting of wood/non wood products

Loss of soil fertility

Varied activities of forest dwellers

Loss of plant/animal resources

2. Grassland Ecosystem 10.6 million ha

Forest tires

Grassland areas further degrades

Kaingin practices

Soil erosion rate (an average

Harvesting of non-timber products

of 73 ha per year)

Mining activities

Increased surface run-off

Herbivore production

Loss of plant/animal resources

Human activities aggravating conditions of watershed areas

3. Freshwater Ecosystem 0.90 million ha


Loss of critical watersheds (19 out of 58)

Operations of mini-hydro power plants


Establishment of swimming resorts using natural springs

Increased silt-load

sedimentation of freshwater

Ecotourism activities

bodies and adjoining zones

Domestic agro-residential industrial sites of water

Affects water quality


Affects yield regulation service for diminishing water agro-industrial-domestic uses; power generation capability


Loss of ecotourism value

Open fisheries

Encroachement of exotic species

Drainage and conversion to agriculture

Loss of native plants/animals

Eutrophication of lakes

Biologically dead rivers; drainage channels

High level of organic and other polluants

4. Rural-urban Ecosystems11.8 million ha

Rural-urban community activities

Affecting life support system

Domestic; agro-industrial production



Lack of quality water


No water

Navigation traffic

Loss of lives, properties and industries

Decreased agricultural and industrial production

5. Mangrove Ecosystems

Mangrove harvesting

Affect mangrove productivity

Remnant 310,375 ha


Decreasing yield of fishery resources,

Land conversion for human settlement areas

Loss of habitat

Loss of nutrients

Conversion of mangrove areas into impoundments for fishy shrimp 210,456 ha

Loss of biodiversity

Conversion of 100,000 ha mangrove swamps into salt beds industrial and agricultural area for coconut and rice production


6. Coral Reef Ecosystems Remnant 2,245 kms

Open fisheries

Affect coral reef productivity

Dynamite fishing

Depletion of economically important fishing grounds

Coral reef harvesting


Muro-ami activities

Loss of biodiversity

Scuba diving


Habitat and niche

Habitat and niche

Habitat = address or home of an organism

· The area where an animal lives or its home, usually an ecosystem or an area within an ecosystem.

· Habitat relates mostly to the non-living physical or chemical conditions of the area such as temperature, rainfall, salinity, sunlight, soil and elevation.

· Habitat and the preservation of biodiversity

· Habitat conservation is directly related to species conservation. The protection of habitats is a more systematic and comprehensive way or preserving species. By protecting any given habitat, a host of species will automatically be protected. This is often more useful than trying to preserve a single species. The loss of habitat is the main cause of species loss in the world. For example, the preservation of mangrove habitat protects those plants and animals that are associated with it.

Niche = occupation of an organism in its community

· A species niche is composed of its habitat, plus the biological or living things found the habitat. The living component (plants and animals) of a habitat is called a community.

· Biological factors include location on the food chain (producers, herbivores, carnivores, etc.) predator/prey relationships and reproductive requirements.

· Interrelationships and interactions are important aspects of niche. For example, tall trees provide shade for plants and animals living under it; birds help disperse seeds of certain trees; and, worms help to aerate the soil.

· Temporal activities are also important in understanding niche. Activities which relate to temporal cycles such as day and night, lunar or seasonal cycles help to define the niche of an organism.

Specialized is generalized niches

Specialized niches apply to species which have very well-defined or narrow physical, biological or chemical requirements for survival. If an organism can only be found within very limited or specific conditions, it is considered to have a very specialized niche. The dugong is an example of an animal with a specialized niche. It requires seagrass beds for food and warm, calm waters for rearing its young. Animals such as the dugong with a specialized niche are more susceptible to extinction than animals with a generalized niche.

Generalized niches apply to species which can exist in a broad range of conditions. Humans are the best examples of species with a generalized niche. In the Philippines, as elsewhere, humans live in diverse conditions with an almost infinite variety of interrelationships. Other animals that are considered to have generalized niches are cockroaches, flies and rats.

Competitive exclusion principle

The fact that no two species can occupy the same niche is called the competitive exclusion principle. For example, two different species of Kingfisher may share the same habitat but may feed on different organisms at different times of the day or in different places.

Niche and ecosystems changes

Understanding the niche of species within an ecosystem will provide insights as to what the consequences of change may be. Two of the more common changes are the elimination of a species and the introduction of exotic or foreign species. The removal of a species whether through extinction or habitat loss can have many undesirable effects. This is often seen when pesticides eliminate beneficial as well as harmful insects. The result can be the removal of an important predator of harmful insects and subsequent increases in the pest population. Understanding the niche of the various organisms in a given habitat will help to predict potential effects of change. The introduction of exotic or non-native species can also bring about detrimental effects. If the introduced species is known to be very resilient and competitive and has a generalized niche, it may colonize-large areas to the detriment of native species. The Eurasian Tree Sparrow is an example of this in the Philippines.

The food chain

The food chain


· All lives exist in an ecological system. Organisms are interrelated by many things. One important relationship among plants and animals is the concept of food chain. Transfer of food energy in which one type of organism consumes another is referred to as the food chain.

· Plants receive energy from the sun and convert it into chemical energy through the process of photosynthesis. Similarly, plants get food from the soil. In both cases of energy transfer from the surf end the soil to the plans, some energy is lost as heat and cannot be used to make the living matter of the plant. Similarly, when plants are eaten by animals, some energy is lost in the transfer of energy from the plants to the animals. Typically, only about 10 percent of the energy is effectively transferred at each link of the food chain. This process can be represented by what is known as the food pyramid.

· All organisms that share the same general types of food in a chain are said to be at the same trophic level. Thus, green plants (producers) occupy the first trophic level, herbivores (primary consumers) occupy the second trophic level, carnivores (secondary consumers) which eat the herbivores occupy the third trophic level and top or secondary carnivores (tertiary consumers)—those that eat other carnivores - occupy the fourth trophic level. The classification of species into trophic levels is based on the function, rather than the species itself. Humans are considered to be omnivores, eating plants, therefore, functioning as a herbivore; and, eating animals, therefore, functioning as a carnivore.

· Food chains are not isolated sequences but are interconnected with one another. The complex series or network of many interconnected food chains is called a food web. Food webs are an important factor for understanding/he importance of maintaining plant and animal diversity in order to protect the interlocking nature of food chains and food webs. As plant and animal species are lost, breaks can occur in the food chain and food web.

· The most obvious form of species interaction in food chains and webs is predation. An individual organism of one species, known as the predator, captures and feeds on parts or all of an organism of another species, the prey. Humans act as predators whenever we eat any plant or animal food.

· An important principle affecting the ultimate population size of an omnivorous species, such as humans, emerges from a consideration of the loss of available energy at successively higher trophic levels in food chains and webs: The shorter the food chain, the less the loss of usable energy. This means that a larger population of humans can be supported if people shorten the food chain by eating grains directly (for example, 1 ha rice = 10 people) rather than eating animals that feed on the grains (grain - cattle - human).

Biological magnification

Biological magnification


· In an ecosystem, any change in the population of one organism is likely to have effects on other organisms in the same food chain or food web.

· This fact is illustrated by what is known as biological magnification. Biological magnification is the increase in concentration of certain fat-soluble chemicals in successively higher trophic levels of a food chain or food web. In other words, as chemical compounds move up through the various links of a food chain by being consumed by different organisms, the toxic effect of these compounds is magnified.

· Biological magnification plays a devastating role in certain types of pollution. Many air end water pollutants are either diluted to relatively harmless levels or are degraded to harmless forms by decomposition and other natural processes. This is true as long as the amount of these chemicals entering the environment is not excessive. However, some synthetic chemicals, such as the pesticide DDT, some radioactive materials and some toxic mercury and lead compounds, become more concentrated in the fatty tissues of organisms at successively higher trophic levels in various food chains and food webs.

· Biological magnification depends on two factors: chemicals that are soluble in fat, but insoluble in water; and, chemicals that either are not broken down or are broken down slowly in the environment.

· To illustrate the process of biological magnification, the example of the pesticide DDT moving through an estuarine ecosystem can be given. DDT is insoluble in water, soluble in fat and breaks down slowly in the environment. Thus, if each phytoplankton concentrates one unit of water-insoluble DDT from the water, a small fish-eating thousands of phytoplankton will store thousands of units of DDT in its fatty tissue. Then, a large fish that eats ten of the smaller fish will receive and store tens of thousands of units of DDT. A bird or human that feeds on several large fish can ingest hundreds of thousands of units of DDT. Of course, ingestion of high levels of DDT in plants and animals, including humans, can lead to chronic health problems and even death.

· Biological magnification of certain chemicals helps explain why dilution is not always the solution to some - forms of air and water pollution.

Nitrogen cycle

Nitrogen cycle


· Living things need nitrogen (N) to manufacture proteins. Plant growth can be limited by a lack of nitrogen available from the soil. Too little nitrogen can also cause malnutrition in humans because many of the body's essential functions require nitrogen-containing molecules, such as proteins.

· The nitrogen cycle outlines the process in which nitrogen is converted into various forms and transported through the biosphere.

· The nitrogen gas which accounts for 78 percent of the volume of the earth's atmosphere is not usable by most plants and animals. Fortunately, the process of nitrogen fixation allows for the conversion of atmospheric nitrogen gas into forms useful to plants. This process is accomplished by soil bacteria; rhizobium bacteria living in root nodules of leguminous plants such as beans, peas and ipil-ipil; blue-green algae such as azolla found in water and soil; lightning; and, industrial manufacture of fertilizers.

· Plants convert nitrates obtained from soil water into large, nitrogen-containing molecules necessary for life and good health. Animals get most of the nitrogen-containing molecules they need by eating plants or other animals that have eaten plants. When plants and animals die, decomposers break down the nitrogencontaining molecules into ammonia gas and other compounds. Other specialized bacteria convert these into soil nitrates and nitrogen gas which is released to the atmosphere to begin the cycle again.

· Humans intervene in the nitrogen cycle in several important ways:

· Large quantities of Nitrous oxide (NO) and Nitrous dioxide (NO2) are added to the atmosphere when fossil fuels are burned in power plants and vehicles. These nitrogen compounds react with other chemicals in the atmosphere to form smog and acid rain, endangering the health of humans.

· Nitrogen gas and hydrogen gas are converted by an industrial process into ammonia gas and then ammonia compounds used as inorganic fertilizers.

· Mineral deposits of compounds containing nitrates are mined and used as inorganic fertilizers.

· Excess nitrates from different sources (e.g., runoff of animal wastes from livestock feedlots, runoff of, inorganic fertilizers from croplands and discharge of treated and untreated sewage) enter aquatic ecosystems, causing rapid growth of algae, depleting the water of dissolved oxygen gas and causing fish kills. This is known as cultural eutrophication, a process that speeds up the natural ageing of lakes.

Society and the carbon-oxygen cycle

Society and the carbon-oxygen cycle

Society and the carbon-oxygen cycle

· Carbon and oxygen are two of the most important elements needed by all living organisms.

· The cycling of carbon and oxygen is closely tied with energy flows in the ecosystem.

· Through the process of photosynthesis, green plants convert carbon from the air (in the form of carbon dioxide) into plans tissue (carbohydrates).

· In the process of respiration, oxygen is absorbed by living organisms from the environment and is utilized by living cells as an oxidizing agent. Carbohydrates are broken down to carbon dioxide and water and released again to the atmosphere.

· In nature, the processes of photosynthesis and respiration balance each other. For a long period of time, the concentration of oxygen in the atmosphere remained at 2 l percent while the concentration of carbon dioxide stabilized at 0.03 percent.

· Present human activities release increasingly more amounts of carbon dioxide into the atmosphere and the balance between these two gases is upset.

· Burning of fossil fuels in automobiles, power plants and industry has resulted in the release of large quantities of carbon dioxide and carbon monoxide into the atmosphere.

· Large quantities of carbon dioxide are also released when agricultural residues are burned.

· The forest is an important carbon sink. Forest conversion means removal of a large volume of vegetation that can absorb carbon dioxide from the atmosphere and release oxygen through the process of photosynthesis. Burning of forests directly releases carbon into the atmosphere.

· This increased concentration of carbon dioxide in the atmosphere may cause global climate change with potentially great repercussions for all living organisms, especially humans.

Health consequences of environmental degradation

Health consequences of environmental degradation


Beware! Nature is fighting back against the abuses we have inflicted upon it. Environmental crisis has set in our midst. The food we eat, the air we breathe end the wafer we drink contain in varying degrees harmful substances or pollutants. The generation of wastes has surpassed the capacity of the land, water and atmosphere to assimilate them.

There are four types of pollution, namely:

1. Air Pollution - undesirable changes in the physical and chemical characteristics of air. Smoke emissions of industrial plants, motor vehicles, methane gas from waste/refuse combustion make the air unclean.

2. Water Pollution - when water contains more harmful bacteria and poisonous chemicals that it can naturally get rid oft The dumping of domestic and industrial wastes in to water bodies, floods, mine fatlings can pollute our waterways.

2. Land/Soil Pollution - when harmful substances are introduced into the soil making it unable to sustain plant life. Use of excessive chemical fertilizers and pesticides depletes nutrients. hardens the texture, increases toxicity, making the soil less productive.

4. Noise Pollution - too loud, so sudden, persistent and unpleasant sounds that become an assault to the body causing mental or physical harm. The roaring of motor vehicles, grating sound of jackhammer, squeaking tires, blaring TV sets, radios and stereos and even loud shouts are noise pollutants.

There are three major factors that affect environmental health which can be manifested by the correlation between and among human behavior, environmental degradation and human health impacts.

Rapid population growth, urbanization and industrialization

· These changes bring about environmental degradation due to:

· population pressure in the cities and its consequences such as insufficient human settlements, conversion of agricultural land at the fringes of cities into human setllement areas, pollution, overcrowding, poor solid waste disposal, poor sewerage system and water shortage;

· health problems in slum areas mount where basic health services cannot satisfactorily address; and,

· conversion of forests to agriculture and other uses which can increase soil erosion, cause landslides and aggravate floods.

Health consequence of environmental degradation

The common health problems/diseases brought about by pollution are:

Air respiratory diseases like asthma, bronchitis, tonsillitis, common coughs and colds, TB, eye, nose and throat irritation, cancers

Water-borne - gastro-intestinal diseases such as cholera, typhoid fever, dysentery, infections, hepatitis, food poisoning and even death (i.e., mercury deposits in kidneys and brain)

Soil-borne - parasitism, malnutrition, skin diseases end cancers.


· The human health consequences do not affect everyone equally.
· Children are more affected by environmental degradation than adults.
· Similarly, the poor are at greater risk than the rich.
· Adult's negligence of the environment is stealing the right of the young to health.

Population and the environment

Population and the environment

Population and the environment

Humankind has been blessed with vast resources upon which it depends. However, unchecked population growth places tremendous demands on mother nature. An increase in population means an increase in the following needs: food, water, energy, clothing, housing, consumer goods, infrastructure all of which can lead to environmental degradation.

Population data

Table 1. Philippine population and annual growth rates. (1970-1990)


Population rate (in millions)

Growth rates (in percent)


36.7 -






















Source: National Census and Statistics Office Survey

Population Impacts

Sheer Numbers

All of toe more than one million Filipinos being added to the country' s population each year have basic needs for food, energy, housing and other necessities. Fulfilling these needs, even at a minimal level, has an impact on the environment. For example, each person needs an average of 2,350 food calories (car) daily to be healthy and productive. These food calories must be produced from existing land and water resources. Where people rely on wood for fuel, each rural resident needs about 7.5 trees annually for fuelwood, or 75 trees per person in a 10-year planting and harvesting cycle.

Multiplying factors

Each individual's impact on the environment is multiplied by his/her level of consumption of natural resources and the level of technology used to support that level of consumption.


Population growth increases the density of urban and rural human settlements beyond the ability of local ecosystems to renew themselves or to absorb wastes. Concentrations of people can overwhelm municipal services such as water supply, sanitation, housing, energy and transportation. This also contributes to many health problems such as tuberculosis, viral infections and other contagious diseases.

Pace of Change

Many developing countries, like the Philippines, can barely keep up with the increasing demand for food, jobs and housing. The pace has forced people to adopt environmentally damaging production methods. Increasing demand for consumer goods and the rising need to strengthen the economy have brought an era of increasing industrialization and urbanization.

Threshold Effects

Threshold effects can either be biological or economic. Biological thresholds stem from the increasing stress that additional humans place on natural ecosystems. For example, a lake may be able to absorb the sewage of 500 people but will suddenly cease to support plants and fish if the polluting population grows to 505 people. Economic threshold effects can cause dramatic increase in costs. As more people require more food, energy, wafer end minerals, these resources become scarce or less accessible; therefore, raising their prices and requiring continuous search for substitutes.

Global-carrying capacity

Global-carrying capacity is defined as the maximum human population that the earth can support indefinitely on a specific resource base, using a specific level of technology. There are physical limits to the carrying capacity of the earth:

· The finite capacity of natural systems to provide food and energy and to absorb wastes

· The amount of greenhouse gases that accumulate in the atmosphere without triggering irreversible climatic changes

· The amount of fresh water available to support humans, other animals and plants

· Grasslands take a year to grow back after overgrazing.

· Fish stocks may take five years to return to previous levels after moderate overfishing.

· Forest ecosystems may take 20 to 100 years to grow back.

· Topsoil takes hundreds of years to form.

· Aquifers can take between one and thousands of years to refill.

· Ultimately, the issue of how humans and the earth can reconcile their compatible needs remains a big challenge.