Ecology is

The study of the distribution and abundance of organisms,

ANDthe flows of energy and materials

between abiotic and biotic components of ecosystems.

Ecology is an integrative/ interdisciplinary science

-Understanding of the biological (biotic) and physical (abiotic) sciences

-Provides a context for the reductionist sciences in biology

-Closely tied to genetics and evolution

-Ecology can be studied at different spatial and temporal scales

-Includes the role of humans in their environment (= global change)

Factors to consider

• Non living (abiotic) factors such as light, temperature, salinity, water, oxygen.

• Living factors (biotic) such as competition, predation, symbiosis, disease, mating, camouflage

Abiotic Factors• Light necessary for photosynthesis,

affects distribution and growth of plant and animals. Adapt to low levels of light.

• Temperature affect metabolic rate, most organisms cannot adapt to extreme temperatures and seasonal changes (eg. Plant wilt, animals hibernate)

• Water necessary for life (metabolism), adquate supply necessary. Xerophytes (plants) and desert animals have adaptations to low levels of water. Hydrophytes are adapted to high water conditions

• Oxygen necessary for metabolism, adaptations to receive oxygen (Pneumatophores in magrove) fishes have gills and come to the surface.

Salinity important for water organisms (high salt, low salt). Microbes have contractile vacuole to pump out excess water. Fishes have adaptations to extreme salinity.

pH value is important, for ponds and streams, the pH value can change whether plants absorb CO2 or give off CO2. (more acidic)

1.1. CamouflageCamouflage

• Cryptic coloration:Cryptic coloration:

a. Hides from predators.

b. Example: English Peppered MothExample: English Peppered Moth

2.2. AposematicAposematic

• Bright colorsBright colors

a. Advertises noxious traitAdvertises noxious trait

b. Example: Monarch ButterflyExample: Monarch Butterfly

3.3. MimicryMimicry

• Two examples:Two examples:

1.1. Mullerian MimicryMullerian Mimicry: when two unpalatable species mimic each other in the same habitat.

2.2. Batesian MimicryBatesian Mimicry: palatable species mimic unpalatable species.

Symbiotic RelationshipsSymbiotic Relationships

• Help structure communities.Help structure communities.

• Three examples:Three examples:

1.1. ParasitismParasitism

2.2. CommensalismCommensalism

3.3. MutualismMutualism

1.1. ParasitismParasitism

• Symbiotic relationship which benefits one benefits one organismorganism and harms the otherharms the other.

• Example:Example:

1.1. Tick on a coyoteTick on a coyote

2.2. Tapeworm in a dogTapeworm in a dog

3.3. Flea on a catFlea on a cat

2.2. CommensalismCommensalism

• Symbiotic relationship which benefits one benefits one organismorganism while the other is unaffectedother is unaffected.

• Example:Example:

1.1. Cattle egrets and cattle in fieldCattle egrets and cattle in field

3.3. MutualismMutualism

• Symbiotic relationship which benefits both benefits both organismsorganisms.

• Examples:Examples:

1.1. Acacia ants and acacia treeAcacia ants and acacia tree

2.2. Termites and gut protozoaTermites and gut protozoa

3.3. Legumes and nitrogen-fixing bacteriaLegumes and nitrogen-fixing bacteria

Scales of Ecological Organization

Organism:

Survival and reproductionunit of natural selection

Scales of Ecological Organization

Individuals

• Important to ecologists who study:– Behavioral ecology

• Feeding patterns of predators feeding optimally

– Symbioses• Lichens are “partnerships” between an alga and a

fungus

Scales of Ecological Organization

Population:

Population dynamicsunit of evolutiondemographysex ratios

Population

• A group of individuals, all belonging to just one species

• A community may have several populations

Scales of Ecological Organization

Community:

Interactions among populationsspecies diversity, trophic dynamicscompetition, succession

Community

• All of the living species in an area

• These species may interact

• DOES NOT include abiotic factors

Scales of Ecological Organization

Ecosystem:

Energy flux andnutrient cycling, primary productivitymaterial fluxes

Ecosystem

• The largest unit of biological organization

• Includes both the biotic (living) and the abiotic (non-living) factors in an area– Biotic: all the plants, animals, bacteria, fungi,

molds– Abiotic: temperature, wind, soil nutrients, fire,

flood, rain

Scales of Ecological Organization

Biosphere:

Global processesincludes biotic and physical systemsoceans, atmosphere, geology

Biosphere

• Includes all of Earth’s resources and life forms

• A large variety of habitats

• Important to ecologists who study distribution of organisms (biogeographers)

the processes and conditions provided by ecosystems that are beneficial to humans and

other organisms

Ecosystem Services

the processes and conditions provided by ecosystems that are beneficial to humans and

other organisms

Ecosystem

-- a community of animals and plants interacting with one another and their

physical environment

-- includes physical and chemical components such as soils, water, nutrients that support the organisms that live within them, ranging from

bacteria to rainforest trees to elephants and humans too

Food Chains and Food Webs

Food Webs

Global Cycles

Ecosystem Ecology

• Definition: All the organisms living in a community AND the abiotic factors with which they interact– Scale depends on questions asked

• One, small habitat, up to –

• The biosphere

– Energy flow through trophic levels– Biogeochemical cycling

• Carbon (climate change)

• Inorganic nutrients (eutrophication)

Ecosystem Dynamics

• Energy flows through ecosystems– ultimately lost as

heat

• Matter cycles around ecosystems– Elements are not

lost but cycle through “pools”

Het

erot

rphs

Fig. 54.1

54.1

PHOTO, chemo Autotrophs

Decomposers

(dead remains)

Fig. 54.1

Energy Flow• 1st Law of Thermodynamics

– Energy is conserved– Ecosystems:

• energy in from outside sources• passed from trophic level to

trophic level

• 2nd Law of Thermodynamics– Energy transformation is not

100% efficient– Ultimately all lost as heat

• Trace energy flow– Outside source to heat– Compute energy budgets at

each transfer

PHOTO, chemo Autotrophs

Decomposers

& dead remains

HEAT OUT

Trophic StructureTrophic Structure

• The different feeding relationshipsdifferent feeding relationships that determine the route of energy flowroute of energy flow and the pattern of chemical cycling.

• According to the “rules of ten,”“rules of ten,” approximately 10% 10% of the potential energyof the potential energy stored in the bonds of organic molecules at one trophic leveltrophic level fuels the growth and growth and developmentdevelopment of organisms at the next trophic leveltrophic level.

Trophic StructureTrophic Structure

• Five examples:Five examples:

1.1. Primary ProducersPrimary Producers

2.2. Primary ConsumersPrimary Consumers

3.3. Secondary ConsumersSecondary Consumers

4.4. Tertiary ConsumersTertiary Consumers

5.5. Decomposers and DetrivoresDecomposers and Detrivores

NICHEIn ecology, a niche is a term describing the relational position of a species or population in an ecosystem. All living things have their niches. A niche is the role and position of a species in nature. Another way of looking at it is that a niche is basically an organism's "job" in nature. Two different populations can not occupy the same niche at the same time, however. The description of a niche may include descriptions of the organism's life history, habitat, and place in the food chain. The full range of environmental conditions (biological and physical) under which an organism can exist describes its fundamental niche. As a result of pressure from, and interactions with, other organisms (e.g. superior competitors) species are usually forced to occupy a niche that is narrower than this and to which they are mostly highly adapted. This is termed the realized niche.

Ecological Adaptations

•     1.   Camouflage (Cryptic)       2.   Disruptive Markings           3.   Warning Coloration           3.   Mating Coloration           5.   Batesian Mimicry           6.   Automimicry       

CamouflageCryptic: Concealing form and coloration which enables a species to avoid its natural predators by camouflage. Good examples of this adaptation are the katydid, walking stick and tomato hornworm. The spittlebug secretes a foamy mass to conceal itself on a branchlet. An interesting resident bird of the alpine tundra is remarkably camouflaged by seasonal coloration. During the summer months the plumage is a mottled brownish color. During winter, when the ground is covered with snow, the plumage is snow white.

Two examples of camouflage in San Diego County: A canyon tree frog (Hyla arenicolor) on granodiorite canyan wall (left) and a desert horned lizard (Phrynosoma platyrhinos) on a sandy riverbed.

Disruptive Markings• Disruptive Markings: The markings on some insects, reptiles and mammals make it difficult

to distinguish them from shadows and branches or from other members clustered together. The stripes on a zebra may appear quite distinctive, but to a colorblind lioness it is difficult to single out an individual zebra among a dense population in the African grasslands.

Warning Colouration• Insects with an obnoxious quality (at least to would-be predators), such as bad taste, bad

smell or powerful sting, often exhibit bright colors to warn of their presence. Warning coloration is well developed in the insect order Hymenoptera, including bees and wasps. Small poison dart frogs of the tropical rain forest also exhibit warning coloration. These frogs contain very toxic neurotoxic alkaloids in their skin. Their coloration (called aposematic coloration) is an adaptation for diurnal foraging in which predators can easily recognize and avoid these posonous amphibians.

Bright colorations among the males of some animals (particularly the plumage of birds) gives the male a definite advantage in sexual selection and mate attraction. Mating coloration and behavior of the most "fit" and aggressive males serves to stabilize the population density because only the most sexually select males are able to mate with females of the species.

Mating Colouration

Left: A male frigatebird (Fregata magnificens) photographed on North Semour Island in the Galapagos Archipelago. The male uses his bright red, inflated throat pouch (gular sac) to attract a female. The male sits in the branches of a tree or shrub and waits for a female to fly over. On sighting a female he turns his head up to expose his red pouch, shakes his wing vigorously and makes a loud, resonating courtship call. If the female is impressed she will land next to him.

Batesian MimicryMimicry: One insect (called a mimic) that is perfectly palatable to its predator

resembles another insect (called the model) that is quite disagreeable to the same predator. There are actually two types of mimicry: Batesian and Mullerian. Mimicry in

which the mimic is essentially defenseless is called Batesian Mimicry. A harmless moth (Aegeria) is a Batesian mimic because it is incapable of stinging another animal,

but yet it resembles the yellow jacket wasp (Vespula). Mimicry in which the mimic shares the same defensive mechanism as the model is called Mullerian mimicry. The

yellow jacket wasp and bumblebee (Bombus) are Mullerian mimics because they both have bright yellow and black colors and use powerful stings as a defensive mechanism.

Automimicry• In automimicry, an animal mimics parts of its own body. For example, some snakes

have a tail that resembles their head and a head that resemble their tail. A predatory bird swooping down on its prey might miss its capture when the prey suddenly moves in an unexpected (backwards) direction. Automimicry is well developed in Malaysian lanternflies of the large insect order Homoptera. Since they are not true flies of the order Diptera, the word fly is not written as a separate word. [If they were true flies, their common name would be written as lantern fly.] Some of these remarkable insects have tails with false eyes and antennae, and heads with false tails. The false tail is actually a long extension of the head between the eyes. What appears to be the front is really the rear end and vice versa. When the insect moves it appears to jump backwards.

POPULATION DYNAMICS

• Introduction to population dynamics

• Intraspecific competition

• Interspecific competition

• Predator – Prey Dynamics

Introduction to Population Dynamics • Our working definition for a population is a group of individuals of the same

species that are capable of interacting with each other in a localised area. Four fundamental processes determine the change in population size (births, deaths, immigrations and emigrations). Knowing this, we can write the fundamental equation of population change as:

• Nt+1=Nt + births - deaths + immigration - emigration.

• This equation reads as: the numbers at time t+1 (Nt+1)are determined by the numbers at time t (Nt) plus births and immigrants - deaths and emigrants. This equation always predicts the population change from one time step to the next. Five concepts are at the centre of population ecology. These are 1) population growth, 2) population equilibrium, 3) limitation, 4) regulation and 5) persistence. Population growth is defined as the change in population size from one generation to the next. A population is at equilibrium if it does not change in size through time. Limitation is the processes that set the equilibrium and regulation is the process by which a population returns to its equilibrium. The regulatory processes act in a density dependent manner. That is deaths increase and/or births decrease with increasing density. Population persistence requires that density dependent processes operate.

Intraspecific Competition

• Intraspecific competition occurs when two or more individuals of the same species strive for the same resource. Intraspecific competition can be of scramble (resources divided equally) or contest (resources divided unequally). Under scramble competition, all individuals suffer equally as resources become depleted. Under contest competition, there are winners and losers. Intraspecific competition has effects on individuals that cascade up to the population level. At the individual level, competition for resources can affect development, fertility and survival. At the population level, intraspecific competition for resources can give rise to "logistic" population growth. However, this density dependence is only a necessary condition for population stability. It is not sufficient to always lead to stable population dynamics. Changes in the strength and/or type of the intraspecific competitive process can lead to a range of population dynamics from stable equilibrium to stable limit cycles and chaos. The effects of intraspecific competition can be observed in many populations. For example, in the winter annual Vulpia fasciculatus increases in density lead to a reduction in seed production. The effect of density dependent regulation leads to a predicted population of about 3,500 plants. Under low seed survival (a density-independent process) the equilibirum population size can be reduced to about 100 plants. This highlights the role that density-dependent and density-independent process have on limiting (setting) the equilibrium of a population.

Interspecific Competition• Interspecific competition when individuals from different species compete for a single

resource. Under interspecifc competition both species may suffer reductions in growth rate or only one species may be affected (amensalism). Extensions of the logistic population growth model show that the effects of interspecific competition can be described by competition coefficients. This is the ratio of the decrease in growth (of species 1) due to species 2:decrease in growth (of species 1) due to species 1. If the ratio is less than one then a species inhibits its population growth more than the population growth of its competitors. Under this condition coexistence is possible. Zero-isoclines and phase-plane analysis can be used to determine the outcome of interspecific competition.

• There are four possibilities: 1) species 1 outcompetes species 2, 2) species 2 outcompetes species 1, 3) the outcome depends on initial abundances of species 1 and 2 and 4) the outcome is coexistence. One prediction is that species that share the same ecological niche can coexist unless the intraspecific competitive effects outweigh the interspecific effects. Additional ecological factors such as the presence of natural enemies (e.g. predators, parasites) or the availability of refuges can mitigate the outcome of interspecific competition. Mechanistic models of interspecific competition predict that the best competitor is the one that is most efficient at harvesting the limiting resource.

Predator – Prey Interactions• The key questions in predator-prey interactions are firstly whether predators limit

prey populations and secondly whether predators regulate prey populations. Two theoretical frameworks have been developed to explore predator-prey interactions. The discrete-time Nicholson-Bailey model was formulated specifically to examine the interaction between insect hosts and their specific natural enemies, parasitic wasps. This model predicts diverging oscillations in the dynamics of host and wasp populations. These oscillations are the result of the lag in the response of the wasp population to changes in the host population (the numerical response). Lotka and Volterra independently formulated a more general continuous-time predator-prey model. This model predicts neutral cycles in which the predator population lags the prey population by 1/4 of a cycle. Again, the oscillatory dynamics arise due to the numerical response of the predator to prey. Although predators limit prey populations, they do not regulate prey to a stable point. Additional ecological processes such as prey intraspecific competition, complex functional responses or prey refuges are necessary for stable predator-prey interactions. More complex predator-prey interactions such as apparent competition, intraguild predation and trophic cascades require an understanding of the processes and mechanisms of predation and interspecific competition.

Population Growth• All populations undergo three distinct phases of their life cycle: • growth • stability • decline • Population growth occurs when available resources exceed the

number of individuals able to exploit them. Reproduction is rapid, and death rates are low, producing a net increase in the population size.

• Population stability is often proceeded by a "crash" since the growing population eventually outstrips its available resources. Stability is usually the longest phase of a population's life cycle.

• Decline is the decrease in the number of individuals in a population, and eventually leads to population extinction.

Factors influencing population growth• Nearly all populations will tend to grow exponentially as long as there are resources

available. Most populations have the potential to expand at an exponential rate, since reproduction is generally a multiplicative process. Two of the most basic factors that affect the rate of population growth are the birth rate, and the death rate. The intrinsic rate of increase is the birth rate minus the death rate.

Two modes of population growth. The Exponential curve (also known as a J-curve) occurs when there is no limit to population size. The Logistic curve (also known as an S-curve) shows the effect of a limiting factor (in this case the carrying capacity of the environment).

Energy flow – Primary production

• Primary Production:– Nonorganic source energy converted to organic chemical

energy by autotrophs– Measurement (per unit area per unit time):

• Energy (Joules / m2 / yr)• Biomass - organic molecule dry weight (g Carbon / m2 / yr)

• Primary production sets the spending limit for the ecosystem’s energy budget– 1 % of the available visible light energy is converted to

chemical energy by photosynthetic organisms!– A few systems depend entirely on chemosynthetic primary

production

54.2

II. Energy and the ecosystem

Primary production: capture of light energy and its conversion into energy of chemical bonds in carbohydrates by plants, algae, and some bacteria

Primary productivity: rate at which primary production occurs

Gross primary productivity (GPP): the total energy assimilated* by plants through photosynthesis

Net primary productivity (NPP): the total energy assimilated by plants through photosynthesis minus energy used in respiration

NPP represents energy in an ecosystem available to consumers

NPP usually expressed in g/m2/year

* incorporation of any material into the tissues, cells and fluids of an organism

1 Primary producer = Autotrophs that support all other trophic levels by synthesizing sugars and other organic molecules using light energy.

Trophic Levels - Definitions

2. Primary consumers = Herbivores that consume primary producers.

3. Secondary consumers = Carnivores that eat herbivores.

4. Tertiary consumers = Carnivores that eat other carnivores.

5. Detritivores = Consumers that derive energy from organic wastes and dead organisms.

II. Energy and the ecosystem

Ecological pyramid of energy width of each bar represents the net production of each trophic level ecological efficiency = % of energy transferred across trophic levels efficiencies are 20%, 15% and 10% between trophic levels

Biomass Pyramid

Trophic pyramids

Fig. 54.11

• Trophic efficiency (TE) = % of production transferred from one trophic level to the next

• TE less than PE because 2 losses aren’t included for PE:– energy produced by the next lower level but not actually consumed– unassimilated food at the present level (lost in urine, feces)

• 80-95% of energy is lost between each level – not consumed, not digested, respired

• Compounding of loss throughtrophic pyramid explains why food webs usually have only four or five trophic levels

Number pyramids

Fig. 54.13

• Predators are usually larger than the prey they eat• Limited biomass at the top of an ecological pyramid is

concentrated in a relatively small number of large individuals• “Top predators” are particularly vulnerable to extinction

Ecological efficiency =

Ratio of net productivity at one trophic level compared to net productivity at the

level below.

Ecological efficiencies are 5-20%

Energy Flow in Ecosystems

Energy flow through trophic levels

• “Secondary production”– Chemical energy in consumer’s food converted to

new chemical energy (growth of new consumer biomass)

– Amount ultimately determined by:• NPP

• Efficiency of energy transfer between trophic levels, usually 5-20%

54.3

• Production efficiency– % of a consumer’s

assimilated food that goes into growth

– Range 1 to 40+ %

– Ex: PE = 33/100=33%

– Unassimilated food doesn’t count in calculation because it is available to other “consumers”

Detritivores

Heat

Secondary Production

Fig. 54.10

eaten by caterpillar

II. Energy and the ecosystem

Only 5% to 20% of energy passes between trophic levels

net production of one trophic level becomes the ingested energy of the next higher level

amount of energy reaching each trophic level depends on …… NPP at the base of the food chain… efficiencies of energy transfer at each trophic level

Ricklefs Fig. 6.2

PE= 1-3%PE= 1-3%

PE= 10%

PE= 40%

Production efficiencies

primary producers = 15-70% of assimilated energy used for maintenance

Energy Budget

herbivores and carnivores = 80-95% of assimilated energy used for maintenance

Net production efficiency (%)=

growth+energy in offspring : assimilated energy

birds < 1%small mammals = up to 6%cold blooded animals = 75%

Energy Budget

General Rules for Energy Flow through Ecosystems

1) Assimilation efficiency increases at higher trophic levels

2) Net and gross production efficiencies decrease at higher trophic levels

3) Ecological efficiencies average about 10%

Thus, only about 1% of NPP ends up as production in the third trophic level

WATER CYCLE

• The Water Cycle (also known as the hydrologic cycle) is the journey water takes as it circulates from the land to the sky and back again.

The Sun's heat provides energy to evaporate water from the Earth's surface (oceans, lakes, etc.). Plants also lose water to the air (this is called transpiration). The water vapor eventually condenses, forming tiny droplets in clouds. When the clouds meet cool air over land, precipitation (rain, sleet, or snow) is triggered, and water returns to the land (or sea). Some of the precipitation soaks into the ground. Some of the underground water is trapped between rock or clay layers; this is called groundwater. But most of the water flows downhill as runoff (above ground or underground), eventually returning to the seas as slightly salty water.

CARBON CYCLE

• Carbon exists in the nonliving environment as: • carbon dioxide (CO2) in the atmosphere and

dissolved in water (forming HCO3−) • carbonate rocks (limestone and coral = CaCO3) • deposits of coal, petroleum, and natural gas

derived from once-living things • dead organic matter, e.g., humus in the soil

• Carbon CycleThe movement of carbon, in its many forms, between the biosphere, atmosphere, oceans, and geosphere is described by the carbon cycle, illustrated in the adjacent diagram. In the cycle there are various sinks, or stores, of carbon (represented by the boxes) and processes by which the various sinks exchange carbon (the arrows).

• We are all familiar with how the atmosphere and vegetation exchange carbon. Plants absorb CO2 from the atmosphere during photosynthesis, also called primary production, and release CO2 back in to the atmosphere during respiration. Another major exchange of CO2 occurs between the oceans and the atmosphere. The dissolved CO2 in the oceans is used by marine biota in photosynthesis.

• Two other important processes are fossil fuel burning and changing land use. In fossil fuel burning, coal, oil, natural gas, and gasoline are consumed by industry, power plants, and automobiles. Notice that the arrow goes only one way: from industry to the atmosphere. Changing land use is a broad term which encompasses a host of essentially human activities. They include agriculture, deforestation, and reforestation.

• Before the Industrial Revolution the release of carbon from fossil fuels was very low.

• Now deforestation and burning of fossil fuels. Has upset the carbon Cycle and caused a sudden increase in atmospheric CO2.

NITROGEN CYCLE

• Nitrogen is essential to all living systems, which makes the nitrogen cycle one of Earth's most important nutrient cycles.

• Eighty percent of Earth's atmosphere is made up of nitrogen in its gas phase.

• Atmospheric nitrogen becomes part of living organisms in two ways. The first is through bacteria in the soil that form nitrates out of nitrogen in the air. The second is through lightning. During electrical storms, large amounts of nitrogen are oxidized and united with water to produce an acid that falls to Earth in rainfall and deposits nitrates in the soil.

• Plants take up the nitrates and convert them to proteins that then travel up the food chain through herbivores and carnivores. When organisms excrete waste, the nitrogen is released back into the environment. When they die and decompose, the nitrogen is broken down and converted to ammonia. Plants absorb some of this ammonia; the remainder stays in the soil, where bacteria convert it back to nitrates. The nitrates may be stored in humus or leached from the soil and carried into lakes and streams. Nitrates may also be converted to gaseous nitrogen through a process called denitrification and returned to the atmosphere, continuing the cycle

• Both atmospheric and soil phases.• Plants can’t use Nitrogen out of the air. It must be in

mineral form.• Ammonium ions (NH4-)• Nitrate ions (NO3-) • Many bacteria and cyanobacteria convert N2 to ammonia

(NH3). This process is called Nitrogen Fixation.• Rhizobium bacteria lives in the root nodules of legumes

(peas, beans) and fixes N2 (symbiosis).• Some nitrogen is also fixed by lightning.• Other bacteria reconverts nitrogen compounds back to N2

gas.

Nitrification• By aerobic bacteria• NH3 NO2

- (ammonia nitrite (toxic)• NO2

- NO3- (nitrate nitrate (plant nutrient))

• Nitrogen compounds usable organic molecules eaten

Ammonification• Decomposers convert complex compounds to

ammonia and ammonium ions.• Denitrification

• Anaerobic bacteria convert N2 compounds to N2

gas and nitrous oxide (N2O) atmosphere

Human Effect on the Nitrogen cycle.

• Nitric acid (HNO3) from acid rain.• Nitrous Oxide from manure and inorganic

fertilizers.• Nitrous Oxide is a greenhouse gas and

depletes the ozone layer.• Mining• Nitrogen runoff into water can trigger algal

blooms. • Eutrophication.

Deforestation• Deforestation is the permanent

destruction of indigenous forests and woodlands. The term does not include the removal of industrial forests such as plantations of gums or pines. Deforestation has resulted in the reduction of indigenous forests to four-fifths of their pre-agricultural area. Indigenous forests now cover 21% of the earth's land surface.

• Deforestation is brought about by the following:• * conversion of forests and woodlands to agricultural land

to feed growing numbers of people;• * development of cash crops and cattle ranching, both of

which earn money for tropical countries;• * commercial logging (which supplies the world market

with woods such as meranti, teak, mahogany and ebony) destroys trees as well as opening up forests for agriculture;

• * felling of trees for firewood and building material; the heavy lopping of foliage for fodder; and heavy browsing of saplings by domestic animals like goats.

• To compound the problem, the poor soils of the humid tropics do not support agriculture for long. Thus people are often forced to move on and clear more forests in order to maintain production.

• CONSEQUENCES OF DEFORESTATION* Alteration of local and global climates through disruption of:

• a) The carbon cycle. Forests act as a major carbon store because carbon dioxide (CO2) is taken up from the atmosphere and used to produce the carbohydrates, fats, and proteins that make up the tree. When forests are cleared, and the trees are either burnt or rot, this carbon is released as CO2. This leads to an increase in the atmospheric CO2 concentration. CO2 is the major contributor to the greenhouse effect. It is estimated that deforestation contributes one-third of all CO2 releases caused by people.

• b) The water cycle. Trees draw ground water up through their roots and release it into the atmosphere (transpiration). In Amazonia over half of all the water circulating through the region's ecosystem remains within the plants. With removal of part of the forest, the region cannot hold as much water. The effect of this could be a drier climate.

• * Soil erosion With the loss of a protective cover of vegetation more soil is lost.

• * Silting of water courses, lakes and dams This occurs as a result of soil erosion.

• * Extinction of species which depend on the forest for survival. Forests contain more than half of all species on our planet - as the habitat of these species is destroyed, so the number of species declines (see Enviro Facts "Biodiversity").

Water pollution is a large set of adverse effects upon water bodies (lakes, rivers, oceans, groundwater) caused by human activities. Although natural phenomena such as volcanoes, storms, earthquakes etc. also cause major changes in water quality and the ecological status of water, these are not deemed to be pollution. Water pollution has many causes and characteristics. Increases in nutrient loading may lead to eutrophication. Organic wastes such as sewage and farm waste impose high oxygen demands on the receiving water leading to oxygen depletion with potentially severe impacts on the whole eco-system. Industries discharge a variety of pollutants in their wastewater including heavy metals, organic toxins, oils, nutrients, and solids. Discharges can also have thermal effects, especially those from power stations, and these too reduce the available oxygen. Silt-bearing runoff from many activities including construction sites, forestry and farms can inhibit the penetration of sunlight through the water column restricting photosynthesis and causing blanketing of the lake or river bed which in turns damages the ecology.

   Principal sources of water pollution are:

• Litter in the Water in the U.K.• industrial discharge of chemical wastes and byproducts • discharge of poorly-treated or untreated sewage • surface runoff containing pesticides • slash and burn farming practice, which is often an element within

shifting cultivation agricultural systems • surface runoff containing spilled petroleum products • surface runoff from construction sites, farms, or paved and other

impervious surfaces e.g. silt • discharge of contaminated and/or heated water used for industrial

processes • acid rain caused by industrial discharge of sulfur dioxide (by burning

high-sulfur fossil fuels) • excess nutrients added by runoff containing detergents or fertilizers • underground storage tank leakage, leading to soil contamination,

thence aquifer contamination.

• Many causes of pollution including sewage and fertilizers contain nutrients such as nitrates and phosphates.  In excess levels, nutrients over stimulate the growth of aquatic plants and algae.  Excessive growth of these types of organisms consequently clogs our waterways, use up dissolved oxygen as they decompose, and block light to deeper waters. This, in turn, proves very harmful to aquatic organisms as it affects the respiration ability or fish and other invertebrates that reside in water.

• When natural bacteria and protozoan in the water break down organic material that is run off into streams, lakes and rivers, they begin to use up the oxygen dissolved in the water.  Many types of fish and bottom-dwelling animals cannot survive when levels of dissolved oxygen drop below two to five parts per million.  When this occurs, it kills aquatic organisms in large numbers which leads to disruptions in the food chain

ContaminantsContaminants may include organic and inorganic substances.Some organic water pollutants are:insecticides and herbicides, a huge range of organohalide and other chemicals bacteria, often is from sewage or livestock operations; food processing waste, including pathogens tree and brush debris from logging operations VOCs (Volatile Organic Compounds, industrial solvents) from improper storage Some inorganic water pollutants include:heavy metals including acid mine drainage acidity caused by industrial discharges (especially sulfur dioxide from power plants) chemical waste as industrial by products fertilizers, in runoff from agriculture including nitrates and phosphates silt in surface runoff from construction sites, logging, slash and burn practices or land clearing sites

• Oil pollution is a growing problem, particularly devestating to coastal wildlife.  Small quantities of oil spread rapidly across long distances to form deadly oil slicks. In this picture, demonstrators with "oil-covered" plastic animals protest a potential drilling project in Key Largo, Florida. Whether or not accidental spills occur during the project, its impact on the delicate marine ecosystem of the coral reefs could be devastating.

Air Pollution

• What is air pollution?

• There are several main types of pollution and well-known effects of pollution which are commonly discussed. These include smog, acid rain, the greenhouse effect, and "holes" in the ozone layer. Each of these problems has serious implications for our health and well-being as well as for the whole environment .

One type of air pollution is the release of particles into the air from burning fuel for energy. Diesel smoke is a good example of this particulate matter . This type of pollution is sometimes referred to as "black carbon" pollution. The exhaust from burning fuels in automobiles, homes, and industries is a major source of pollution in the air.

Another type of pollution is the release of noxious gases, such as sulfur dioxide, carbon monoxide, nitrogen oxides, and chemical vapors. These can take part in further chemical reactions once they are in the atmosphere, forming smog and acid rain.

• Smog is a type of large-scale outdoor pollution. It is caused by chemical reactions between pollutants derived from different sources, primarily automobile exhaust and industrial emissions. Cities are often centers of these types of activities, and many suffer from the effects of smog, especially during the warm months of the year.

• Another consequence of outdoor air pollution is acid rain. When a pollutant, such as sulfuric acid combines with droplets of water in the air, the water (or snow) can become acidified . The effects of acid rain on the environment can be very serious. It damages plants by destroying their leaves, it poisons the soil, and it changes the chemistry of lakes and streams. Damage due to acid rain kills trees and harms animals, fish, and other wildlife.

• The Greenhouse Effect, also referred to as global warming, is generally believed to come from the build up of carbon dioxide gas in the atmosphere. Carbon dioxide is produced when fuels are burned. Plants convert carbon dioxide back to oxygen, but the release of carbon dioxide from human activities is higher than the world's plants can process. The situation is made worse since many of the earth's forests are being removed, and plant life is being damaged by acid rain. Thus, the amount of carbon dioxide in the air is continuing to increase. This buildup acts like a blanket and traps heat close to the surface of our earth. Changes of even a few degrees will affect us all through changes in the climate and even the possibility that the polar ice caps may melt.

• Ozone depletion is another result of pollution. Chemicals released by our activities affect the stratosphere , one of the atmospheric layers surrounding earth. The ozone layer in the stratosphere protects the earth from harmful ultraviolet radiation from the sun. Release of chlorofluorocarbons (CFC's) from aerosol cans, cooling systems and refrigerator equipment removes some of the ozone, causing "holes"; to open up in this layer and allowing the radiation to reach the earth. Ultraviolet radiation is known to cause skin cancer and has damaging effects on plants and wildlife

Conservation

• Conservation biology is the protection and management of biodiversity that uses principles and experiences from the biological sciences, from natural resource management, and from the social sciences, including economics. The conservation movement seeks to protect plant and animal species as well as the habitats they live in from harmful human influences . The term "conservation biology" refers to the science and sometimes is used to encompass also the application of this science. The concern of this branch of biology is to help save the diversity of life on Earth through applied conservation research. In the realm of research, biologists seek creative and effective ways to address a wide diversity of ecological problems, ranging from endangered species to regional conservation planning. This translates to developing better conservation tools, analyses, and techniques.

Good conservation policy• Protection laws for sustainable areas to support viable populations.• Limit use of areas for particular industrial/resource use• Prohibit importing of foreign plants/animals, control measures• Pest education about dumping of household garden refuse.• Captive breeding programs• Feral pests/disease controls• Reduction of introduced species, removal of these animals from areas• Sufficient water levels/waterways for natural fish movement.• Rehabilitation of degraded area• Limit human use and impact on these areas• Ongoing research on factors affecting these areas• Animal/plant control, firefighting, education and sufficient funds for these activities• National parks, nature reserves• Culling programs• Decrease and control pollution/dumping into natural waterways• Control gas emissions and burning• Control use of chemical affecting the environment, increase awareness

Land clearing

Ecological impact of clearing land• Breaks landscape into isolated areas that are not sustainable• Affects water movement – increase run off from surface and

waterways• Increase erosion by wind and water• Affects water table increasing soil salinity and waterlogging• Breakdown of soil structure and nutrient depletion• Desertification and local climate change• Decreased bio-diversity and increase danger of extinction

Reafforestation

Reafforestation reasons

Reduce soil salinity, water tables

Prevent erosion, nutrient leeching

Conserve endangered species, biodiversity

Aesthetics (picnic areas, natural beauty)

Improve water quality (reservoir)

Reestablish area after logging, mining

Cultural heritage issues

Ethics – rights to destroy other species?

Ecosystem stability – food web, nutrient

cycles, mutalism, clean air

Source of medicines or industrial raw materials

Reafforestation program features

Survival of species adapted to that area

Species with high rate of survival

Local species to support local animal populations

Disease resistant strains

Variety of species that naturally grow together.