At each trophic level, toxic substances (Hg, pesticides, TCDD, etc.) become more concentrated 1. Biomagnification
Ultraviolet Radiation and the Ozone Layer
With a depleted ozone layer, more UV radiation will reach the surface of Earth
This will cause an increase in many problems, including cancer, will affect crops, damage phytoplankton and zooplankton
2. Ozone Depletion
Stratospheric ozone continues to decline
Ozone is a natural component of the stratosphere
Ozone shields the surface of the Earth from UV radiation
Ozone depletion has appeared over Antarctica most demonstrably first in 1984
2. Ozone Depletion
Certain chemicals destroy stratospheric ozone
Chlorofluorocarbons ( CFCs) are broken down by UV in the stratosphere and react with ozone, forming molecular oxygen
CFCs are not used up in this reaction, and are able to break down many thousands of ozone molecules
Ozone Depletion Is Harmful
Ozone depletion harms living organisms
Exposure to UV is linked to disorders in humans, including cataracts, skin cancer, and weakened immune systems
Exposure to increasing UV is linked to declines in phytoplankton productivity
Basal Cell Skin Cancer
6% Declines in phytoplankton over the last 10 years map right: Satellites Many of the areas showing an increasing trend appear along the coasts, in red, while most of the dark blue areas indicate a decreasing trend. Units for the top two panels are milligrams of chlorophyll per cubic meter.
International cooperation (the Montreal Protocol) will prevent significant depletion of the ozone layer
Despite agreements to decrease CFC production, ozone depletion has continually worsened
Freon is a trade name for a group of chlorofluorocarbons used primarily as a refrigerant.
One major use of CFCs has been as propellants in aerosol inhalers for drugs used to treat asthma.
3. Acid Rain Global Sulfur Cycle
Causes of Acid Rain
Burning coal. Oil and natural gas in power stations makes electricity, giving off sulphur dioxide gas.
Burning petrol and oil in vehicle engines gives off nitrogen oxides as gases.
These gases mix with water vapour and rainwater in the atmosphere producing weak solutions of sulphuric and nitric acids – which fall as acid rain.
The Sulfur Cycle 1
Sulfur is an essential element and, like nitrogen, has many oxidation states and follows complex chemical pathways.
Sulfur reduction reactions include:
assimilatory sulfate reduction to organic forms and dissimilatory oxidation back to sulfate by many organisms
reduction of sulfate when used as an oxidizer for respiration by heterotrophic bacteria in anaerobic environments
The Sulfur Cycle 2
Sulfur oxidation reactions include:
oxidation of reduced sulfur when used as an electron donor (in place of oxygen in water) by photosynthetic bacteria
oxidation of sulfur by chemoautotrophic bacteria that use the energy thus obtained for assimilation of CO 2
Acid rain can travel long distances.
Often it doesn’t fall where the gas is produced. High chimneys disperse (spread) the gases and winds blow them great distances before they dissolve and fall to Earth as rain.
Eg. gases produced in England and Western Europe can result in acid rain in Scotland and Scandinavia.
Acid Rain and Forest Decline
Acid Rain and Forest Growth
Decline in forests, noted in northeastern US and central Europe in the 1960s, appeared correlated with acid rain.
The Clean Air Act of 1970 reduced emissions of sulfur oxides and particulates in the US.
Forests did not show signs of recovery. Why?
Slow Recovery of Forests from Effects of Acid Rain
Studies at Hubbard Brook Experimental Forest in New Hampshire showed why forests did not recover after passage of Clean Air Act:
acidity of rain declined slowly
emissions of particulates declined, reducing an important source of calcium at Hubbard Brook
leaching of calcium and other nutrients by acid rain left lasting effects on soil fertility
Acid Rain Effects
How Acid Rain Affects The Environment
Acid rain is an extremely destructive form of pollution, and the environment suffers from its effects. Forests, trees, lakes, animals, and plants suffer from acid rain. Trees
The needles and leaves of the trees turn brown and fall off.
Trees can also suffer from stunted growth; and have damaged bark and leaves, which makes them vulnerable to weather, disease, and insects.
All of this happens partly because of direct contact between trees and acid rain, but it also happens when trees absorb soil that has come into contact with acid rain.
The soil poisons the tree with toxic substances that the rain has deposited into it.
Lakes are also damaged by acid rain. Fish die off, and that removes the main source of food for birds. Acid rain can even kill fish before they are born when the eggs are laid and come into contact with the acid.
Fish usually die only when the acid level of a lake is high; when the acid level is lower, they can become sick, suffer stunted growth, or lose their ability to reproduce.
Also, birds can die from eating "toxic" fish and insects.
Acid rain dissolves the stonework and mortar of buildings (especially those made out of sandstone or limestone).
It reacts with the minerals in the stone to form a powdery substance that can be washed away by rain.
Transport Currently, both the railway industry and the aeroplane industry are having to spend a lot of money to repair the corrosive damage done by acid rain. Also, bridges have collapsed in the past due to acid rain corrosion.
Humans can become seriously ill, and can even die from the effects of acid rain. One of the major problems that acid rain can cause in a human being is respiratory problems.
Many can find it difficult to breathe, especially people who have asthma. Asthma, along with dry coughs, headaches, and throat irritations can be caused by the sulphur dioxides and nitrogen oxides from acid rain.
Acid rain can be absorbed by both plants (through soil and/or direct contact) and animals (from things they eat and/or direct contact). When humans eat these plants or animals, the toxins inside of their meals can affect them. Brain damage, kidney problems, and Alzheimer's disease has been linked to people eating "toxic" animals/plants.
Research carried out in North America in 1982, revealed that sulphur pollution killed 51,000 people and about 200,000 people become ill as a result of the pollution.
What are the solutions to acid rain?
Sulphur dioxide can be removed from power stations chimneys but this process is expensive.
2. Reduce the amount of electricity we use
turn tv’s off at the mains, don’t leave on standby.
turn off lights when a room is not in use.
3. Use renewable energy like wind power, solar panels, tidal power, HEP schemes and geothermal energy.
4. Fit catalytic converters to vehicle exhausts which remove the nitrogen oxides.
5. Limit the number of vehicles on the roads and increase public transport.
Since the Industrial Revolution Concentration of Carbon Dioxide from trapped air measurements for the DE08 ice core near the summit of Law Dome, Antarctica. (Data measured by CSIRO Division of Atmospheric Research from ice cores supplied by Australian Antarctic Division)
Biological extinction is the eventual fate of all species, but humans are greatly increasing the extinction rate
According to the United States Endangered Species Act, a species is declared endangered when it is in danger of becoming extinct
A threatened species is one in which the population has become greatly diminished and will probably become endangered
5. Declining Biological Diversity
Humans Contribute to Declining Biological Diversity
Fragmentation of habitat for housing, agriculture leads to species decline
Pollution greatly affects populations
Introduction of exotic species harms native species due to competition, predation, or interbreeding
The zebra mussel from the Caspian, introduced into the American Great Lakes These
mussels not only cause billions of
dollars of damage but have
displaced the native clams and
The ctenophore Mnemiopsis , introduced to the Black Sea and Caspian •Island populations are particularly sensitive to introductions. The introduction of goats to Abingdon island in the Galapagos wiped out the abingdon tortoise
5. Declining Biological Diversity continued
Some species have become endangered or extinct by deliberate human action to eradicate them
Prairie dogs, wolves, mountain lions and grizzly bears
Commercial hunting, sport hunting and subsistence hunting has led to the decline or extinction of many birds and large mammals
Commercial harvesting removes live animals and plants from the wild for research, zoos, and the pet trade
The dusky seaside sparrow became extinct in 1987, primarily due to human destruction of its habitat in Florida
The Conservation of Biodiversity
Biodiversity is highest in the tropical Rainforest
Ethical reasons for conserving biodiversity are that all species have a right to live on this planet.
Ecological reasons are that species live with great interaction and dependence on each other. If one species dies out, a food chain is disrupted, therefore disrupting all of the other species as well.
Economic reasons are that the rainforest is a source of materials important to human life. Medicinal substances can be taken from a variety of plants in the rain forest, and ecotourism offers a new source of funds for the many impoverished nations these forests exist in.
Aesthetic reasons are that the tropical rain forest is one of the most beautiful attractions on this planet. There is variety everywhere in the rainforest.
Factors that caused the extinction of one animal
The Arizona Jaguar became
extinct due to an increased
demand for its fur. As the
human population increased
in the areas inhabited by the
jaguar, the hunting and
shooting increased and the
last of this rare animal was
shot in 1905.
Factors that caused the extinction of one plant
In New Mexico. The Fluffy groundsel
is a kind of herbal plant with clusters
of yellow flowers. It became extinct
because of farming, building, road
construction and other sorts of
human impact in the American
Simpson diversity index
The index of diversity is used as a measure of the range and numbers of species in an area. It usually takes into account the number of species present and the number of individuals of each species. It can be calculated by the following formulae:
D = N(N-1) ∑n(n-1)
D= Diversity index
n = number of individuals of a each species found in an area.
N = total # of organisms of all species found in an area.
The simpson diversity index is a measure of species richness.
A high value of D suggests a stable and ancient site.
Comparing both indices, 6.05 is an indicator of greater
diversity. The higher number indicates greater diversity
In extreme environments the diversity of organisms is usually low (has a low index number). This may result in an unstable ecosystem in which populations are usually dominated by abiotic factors . The abiotic factor(s) are extreme and few species have adaptations allowing them to survive. Therefore food webs are relatively simple, with few food chains, or connections between them – because few producers survive. This can produce an unstable ecosystem because a change in the population of one species can cause big changes in populations of other species.
In less hostile environments the diversity of organisms is
usually high (high index number). This may result in a
stable ecosystem in which populations are usually dominated
by biotic factors , and abiotic factors are not extreme. Many
species have adaptations that allow them to survive,
including many plants/producers. Therefore food webs are
complex, with many inter-connected food chains. This
results in a stable ecosystem because if the population of
one species changes, there are alternative food sources for
populations of other species.
The use of biotic indicator for monitoring environmental change
Are a good indicator of change
Highly sensitive to environmental changes
Highly sensitive to population increases or decreases.
The numbers of organisms in the indicator species populations, can be measured directly so they are easy to keep track of larger changes that maybe occurring.
Feeds on aquatic insects and their larvae, including dragonfly, nymphs and caddisfly larvae. It may also take tiny fish.
The presence of this indicator species shows good water quality; it has vanished from some locations due to pollution or increased silt load in streams
Human Effect on the World Fish Population
Overexploitation of species affects the loss of
genetic diversity and the loss in the relative
species abundance of both individual and/or groups of interacting species. Overexploitation may include over fishing and over harvesting
Historically, humans have fished the oceans, which never seemed to pose a problem due to their abundant resources. Gear (fish trap, gill nets, electro-fishing) and vessel efficiency modifications have caused a significant decrease in fish populations.
Population dynamics of fisheries
A fishery is an area with an associated fish population which is harvested for its commercial or recreational value. Fisheries can be wild or farmed.
Population dynamics describes the ways in which a given population grows and shrinks over time, as controlled by birth, death, and emigration or immigration. It is the basis for understanding changing fishery patterns and issues such as habitat destruction, predation and optimal harvesting rates.
The population dynamics of fisheries is used by fisheries scientists to determine sustainable yields
Estimating Fish populations
Virtual Population Analysis is a modeling technique commonly used in fisheries science for reconstructing fish numbers using information on death of individuals each year. This death is usually partitioned into catch by fishing industry and natural mortality.
Capture-Mark-Recapture Method day one, mark and release the fish. The next day, repeat the sequential sampling and also records the total number of fish marked and unmarked so we can use to estimate of fish population density.
The overall catch has decreased fish stocks in many areas of the United States, as catches in each area exceed the maximum number of fish that these fishermen are allowed to take.
Though fish farming is increasing, fishing represents the last major exploitation of wild populations by mankind
ACEL Factory ship
A case study: The Peruvian Anchovy ( Engraulis ringens ) Universidad de La Serena
The Peruvian Anchovy
This is a small (12-20cm), short-lived species maturing in 1 year
Anchovy live in the surface waters in large shoals off the coast of Peru and northern Chile
Here there are cold currents up-welling from the sea bed bringing nutrients for phytoplankton
Plankton is at the base of the food chain.
The Peruvian Anchovy
The harvest of this fish doubled every year from 1955 to 1961
Experts estimated the maximum harvestable yield ( MSY ) at 10 to 11 million tonnes per year
Through the 1960s the harvest was about this level
The biggest fishing harvest in the world
Some of the anchovy were used for human food
But a lot was ground into fishmeal for animal feed
The collapse of the anchovy fishery
In 1972 there was an El Ni ñ o event that brought warm tropical water into the area
The up-welling stopped,
the phytoplankton growth decreased
the anchovy numbers fell and concentrated further south
The concentrated shoals of anchovy were easy targets for fishing boat eager to recuperate their harvest
The political will was not there to impose reduced quotas
Larger catches were made
No young fish were entering the population (no recruitment)
No reproduction was taking place
The fish stocks collapsed and did not recover
What is causing the damage to fisheries worldwide?
What is causing the damage to fisheries worldwide?
Several reasons frequently are listed as causes
for the decline:
Habitat Alterations Anadromous species (shad, herring, striped bass) - dam construction, river flow too high or low, interferes with eggs development
Water Quality and Pollution Problems causes declines in spawning areas (low dissolved oxygen for shad)
Over-harvest Uncontrolled harvesting – even if quotas are imposed they need to be policed. This a lead to declines in as an example, shad, striped bass, oysters
What is causing the damage to fisheries worldwide?
Unrealistic and inflexible quotas
Insufficient data on fish populations
Improved technology in the fishing industry
Fish populations are reduced below their recovery level
Other non-commercial species are being taken and killed at the same time
Other species (e.g. sea birds) are being deprived of a food resource
Total ban on some species now imposed: Peruvian anchovy Pacific salmon Newfoundland, Grand Banks cod North Sea Herring
Maximum Sustainable Yield (MSY)
the harvest rate
2. the recruitment rate of new (young) fish into the population
a population can be harvested at the point in their population growth rate where it is highest (the exponential phase)
Harvesting (output) balances recruitment (input)
Fixed fishing quotas will produce a constant harvesting rate (i.e. a constant number of individuals fished in a given period of time)
Maximum Sustainable Yield (MSY) K
Time 1 2 3
Problems with MSY
Age structure : If all the age groups are harvested recruitment of young fish into the reproductive group will be reduced. The answer is to use a net with a big enough mesh size that lets the young fish escape
Limiting factors : If the limiting factors in the environment change so does the population growth rate
Limiting factors set the carrying capacity (K) of an environment
Increasing limiting factors will cause K to drop
Fixed quotas cannot cope with this
Data: For MSY to work accurate data in fish populations is needed (population size, age structure, recruitment rates)
Usually these are not well known
What is required?
Nets with bigger mesh size
Regulated fishing methods
More data on fish populations (e.g. by fish tagging investigations – mark and recapture)
Constant monitoring to observe changes in environmental factors (e.g.El Ni ñ o events
Policing of fishing industry – respect of quotas
Greater exploitation of fish farming
But this is not without its own problems (space, diseases and pollution are all associated with intensive fish culture)
In situ Ex situ
In situ :
Conservation of species in their natural habitat
E.g. natural parks, nature reserves
Ex situ :
Conserving species in isolation of their natural habitat
E.g. zoos, botanical gardens, seed banks
In situ conservation
Setting up wild life reserves is not just a matter of building a fence around an area and letting it grow “wild”
Without grazing animals heathlands which contain a number of rare species will revert to woodland
Nature reserves and national parks
First the area that is suitable for the creation of a reserve has to be identified and delimited
This requires surveys to collect data on key species
Property may have to be expropriated
A legal framework may need to be set up to control human activities in the area and in it’s immediate surroundings
Policing the area may also be necessary
Les Ecrins National Park, France Park Park Buffer zone
Nature reserves and national parks
If part of the area has been degraded due to bad land use it may need restoring
Alien species that have penetrated the area may need excluding or eliminating
Constant management will be needed to maintain the habitat of the species being conserved
This may mean arresting natural succession
The advantages of in situ conservation
The species will have all the resources that it is adapted too
The species will continue to evolve in their environment
The species have more space
Bigger breeding populations can be kept
It is cheaper to keep an organism in its natural habitat
However there are problems
It is difficult to control illegal exploitation (e.g. poaching)
The environment may need restoring and alien species are difficult to control
Ex situ conservation Captive breeding
The Hawaiian goose was practically extinct in the wild
12 birds were taken into captivity
A population of 9000 was released back into the wild
The experiment failed because the original cause rats had not been eliminated.
The rats eat the eggs and the nestlings of the geese
State Symbols USA
Pere David’s deer success or failure?
Pere David’s deer was a native species of China
In 1865 18 were taken into zoological collections
Meanwhile it became extinct in the wild
By 1981 there were 994 individuals scattered through zoological collections
Ex situ conservation
Captive breeding of endangered species is a last resort
These species have already reached the point where their populations would not recover in the wild
It works well for species that are easily bred in captivity but more specialised animals are difficult to keep (aye aye)
Isolated in captivity they do not evolve with their environment
Zoos: The land of the living dead?
They have a very small gene pool in which to mix their genes
Inbreeding is a serious problem
Zoos and parks try to solve this by exchanging specimens or by artificial insemination where it is possible
In vitro fertilization and fostering by a closely related species has even been tried (Indian Guar – large species of cattle - cloned)
Even if it is possible to restore a population in captivity the natural habitat may have disappeared in the wild
Species that rely on this much help are often considered to be “the living dead”
Botanical gardens show the same problems as captive breeding of animals
Originally the role of botanical gardens was economic, pharmaceutical and aesthetic
There range of species collected was limited
The distribution of botanical gardens reflects the distribution of colonial powers
Most are found in Europe and North America
But plant diversity is greatest in the tropics
Seeds can be maintained for decades or even centuries if the conditions are controlled
<5% humidity and –20°C
Not all species are suited to this treatment
Seeds need to be regularly germinated to renew stock or the seeds will eventually loose their viability
Seed banks are at risk from power failure, natural disasters and war
Duplicate stocks can be maintained
Seeds kept in seed banks do not evolve with changes in the environment
The doomsday vault - Spitzbergen Bergen Nat Acc of Arts BBC
CITES (The Convention in International Trade in Endangered Species)
Set up in 1988 to control and encourage the sustainable exploitation of species
The CITES conferences determine the status of a species and whether or not its exploitation requires regulation
Species are placed into different appendices depending on their status
Appendix 1: Total ban on exploitation
Appendix 2: Limited exploitation subject to quotas
Appendix 3: Species requiring protection in certain states only
Species are reassessed every 2 years
WWF (World Wide Fund for Nature formerly World Wildlife Fund)
Set up in 1961 as a non-governmental organisation
Raises funds for conservation
Lobbies parliaments for conservation
Runs education programmes
Provides advice to government conservation agencies