Succession

SuccessionSuccession

The non-seasonal, directional (time) The non-seasonal, directional (time) change in community within a habitatchange in community within a habitat

Unstable r-strategists Unstable r-strategists stable K-stable K-strategistsstrategists

Primary succession is the series of community changes which occur on an entirely new habitat which has never been colonized before.

Examples of such habitats would include newly exposed or deposited surfaces, such as landslips, volcanic lava and debris, elevated sand banks and dunes, quarried rock faces.

A number of stages (seres) will take place in which an initial or 'pioneer' community will gradually develop through a number of different seres, into a 'climax' community, which is the final stage.

Secondary succession is the series of community changes which take place on a previously colonized, but disturbed or damaged habitat. Examples include areas which have been cleared of existing vegetation (such as after tree-felling in a woodland) and destructive events such as fires.

Secondary succession is usually much quicker than primary succession for the following reasons:

•There is already an existing seed bank of suitable plants in the soil.

•Root systems undisturbed in the soil, stumps and other plant parts from previously existing plants can rapidly regenerate.

•The fertility and structure of the soil has also already been substantially modified by previous organisms to make it more suitable for growth and colonization.

As a result of SuccessionAs a result of Succession– Stability increases (r Stability increases (r K) K)– Diversity increasesDiversity increases

2 types:2 types:– Primary - from bare rock (Xerarch)Primary - from bare rock (Xerarch)– Secondary – from a disturbed habitat e.g. water course Secondary – from a disturbed habitat e.g. water course

silting (Hydrarch)silting (Hydrarch) 2 mechanisms:2 mechanisms:

– Autogenic – changes are caused by the organisms Autogenic – changes are caused by the organisms themselves e.g. lichenthemselves e.g. lichen

– Allogenic - change is elicited by external agency e.g. Allogenic - change is elicited by external agency e.g. climatic event, landslide, climatic event, landslide, human interventionhuman intervention

Human Impact on EcosystemsHuman Impact on Ecosystems

Man impacts environments for a number of Man impacts environments for a number of reasons:reasons:– Food production – agriculture and wild harvestFood production – agriculture and wild harvest

– Energy productionEnergy production

– PollutionPollution

Together these activities stress ecosystemsTogether these activities stress ecosystems Stress leads to a reduction in species diversityStress leads to a reduction in species diversity

– Populations sizes may increase (lack of Populations sizes may increase (lack of interspecific competition)interspecific competition)

Human Impact on Ecosystems Human Impact on Ecosystems – Food Production– Food Production

““The battle to feed humanity is over. In The battle to feed humanity is over. In the course of the 1970’s the world will the course of the 1970’s the world will experience starvation of tragic experience starvation of tragic proportions – hundreds of millions of proportions – hundreds of millions of people will die.” – Paul Ehrlich, people will die.” – Paul Ehrlich, The The Population time BombPopulation time Bomb, 1968., 1968.We now have more food than ever before

- Improved irrigation and farming methods

- High yield crops

- Fertilizers & pesticides

What Cost?

Effects of Intensive food Production-Effects of Intensive food Production-ProblemsProblems

MonocultureMonoculture– growing a single species over a large area – trees/ growing a single species over a large area – trees/

food cropsfood crops» Loss of habitat including increase in field size for Loss of habitat including increase in field size for

efficiencyefficiency Reduces species diversityReduces species diversity

» Loss of nutrients – leaching due to soil erosionLoss of nutrients – leaching due to soil erosion» Invasion of opportunistic weedsInvasion of opportunistic weeds» Intensification of disease/ predation problemsIntensification of disease/ predation problems» Loss of soil structure due to inorganic fertilisers leads to Loss of soil structure due to inorganic fertilisers leads to

topsoil erosiontopsoil erosion

Effects of Intensive food Production - Effects of Intensive food Production - SolutionsSolutions

CHEMICALSCHEMICALS– Herbicides (weedkillers, natural/ synthetic)Herbicides (weedkillers, natural/ synthetic)– Pesticides (insecticides & fungicides Pesticides (insecticides & fungicides

natural/synthetic)natural/synthetic)– Fertilisers (NPK & organic)Fertilisers (NPK & organic)

DIFFICULTIESDIFFICULTIES– Toxicity (to consumer & non target species)Toxicity (to consumer & non target species)– Bioaccumulation through food chain (leading to Bioaccumulation through food chain (leading to

toxicity)toxicity)– Resistance requiring stronger chemicalsResistance requiring stronger chemicals– PersistencePersistence– Pollution (leaching/ runoff)Pollution (leaching/ runoff)

Examples - FertilisersExamples - Fertilisers

Fertilisers (organic or NPK)Fertilisers (organic or NPK)– Eutrophication excessive nutrients into Eutrophication excessive nutrients into

water (deoxygenation)water (deoxygenation)– Nitrate in water – blue baby syndrome due Nitrate in water – blue baby syndrome due

to nitrite oxidation of haemoglobinto nitrite oxidation of haemoglobin– Cancer – not certainCancer – not certain

Examples - PesticidesExamples - Pesticides

Pesticides can be toxic to man and other Pesticides can be toxic to man and other speciesspecies

DDT/DDE – synthetic oestrogenDDT/DDE – synthetic oestrogen– thin egg shell - birds of preythin egg shell - birds of prey

– altered sex ratio (small penis, testiclesaltered sex ratio (small penis, testicles» RATS, alligators, fishRATS, alligators, fish

– Link to breast cancer Link to breast cancer

– Fall in sperm counts (controversial - sex more Fall in sperm counts (controversial - sex more often)often)

– Organic farmers better sperm quality (Denmark)Organic farmers better sperm quality (Denmark)

Examples - HerbicidesExamples - Herbicides

Kill indiscriminatelyKill indiscriminately– Good & bad weeds killedGood & bad weeds killed– Loss of food/ habitat for variety of animalsLoss of food/ habitat for variety of animals– Loss of food web diversity – unstableLoss of food web diversity – unstable– Loss of useful insect etc. speciesLoss of useful insect etc. species– Loss of soil improving microbes/ animalsLoss of soil improving microbes/ animals

Possibly toxicPossibly toxic

Increasing Energy NeedsIncreasing Energy Needs

Energy requirements have increasedEnergy requirements have increased Principally they have been met by Principally they have been met by

polluting fossil fuelspolluting fossil fuels This has lead to carbon dioxide This has lead to carbon dioxide

emissions increasing substantiallyemissions increasing substantially

Carbon dioxide causes GLOBAL WARMING

Global WarmingGlobal Warming

Principally due to carbon dioxide (60%)Principally due to carbon dioxide (60%)– Other gases includeOther gases include

» MethaneMethane (20%)(20%)

» CFCsCFCs (14%)(14%)

» Nitrogen OxidesNitrogen Oxides (6%)(6%)

» Ozone (upper atmosphere) (8%)Ozone (upper atmosphere) (8%)

Carbon dioxide has increased by 31% Carbon dioxide has increased by 31% during industrial revolutionduring industrial revolution– Increase due to combustion, deforestationIncrease due to combustion, deforestation

Climate change solutionsClimate change solutions

Change of 0.6Change of 0.6°°C over last centuryC over last century– Projected rise 1.5 Projected rise 1.5 °° -4.5 -4.5 °° C C– Not all due to Carbon Dioxide, sunspot Not all due to Carbon Dioxide, sunspot

activityactivity SolutionsSolutions

– Reduce fossil fuel combustionReduce fossil fuel combustion– Switch to alternative fuel sources Switch to alternative fuel sources

(renewable)(renewable)

Conserve forestsAdd iron to sea

Global Warming ProblemsGlobal Warming Problems

Coral bleachingCoral bleaching– Loss of photosynthetic algae (zooxanthellae) from Loss of photosynthetic algae (zooxanthellae) from

commensal relationship due to 1commensal relationship due to 1°°C increase in sea C increase in sea temperaturetemperature

Disease spreadDisease spread– Malaria possible in south britainMalaria possible in south britain

Loss of species’ nichesLoss of species’ niches– e.g. arctic species on cairngormse.g. arctic species on cairngorms

http://www.metoffice.gov.uk/research/hadleycentre/models/modeldata.html

Food production Food production needs to double needs to double to meet the to meet the needs of an needs of an additional 3 additional 3 billion people in billion people in the next 30 the next 30 yearsyears

Climate change is projected to decrease agricultural productivity in the tropics and sub-tropics for almost any amount of warming

Other Pollution from Other Pollution from combustion of fossil fuelscombustion of fossil fuels

Acid rain (SOAcid rain (SO22, No, Noxx))

– Other pollutants Other pollutants » PM 10s - AsthmaPM 10s - Asthma

Ozone layerOzone layer– CFCs activated by high energy photonsCFCs activated by high energy photons– Chlorine free radicals react with ozone in Chlorine free radicals react with ozone in

upper atmosphereupper atmosphere

PollutionPollution

Heavy metalsHeavy metals– Interfere with enzyme action/ biochemical Interfere with enzyme action/ biochemical

processesprocesses– Result of industrial activity, common at Result of industrial activity, common at

foundry sites/ gas worksfoundry sites/ gas works– Can be removed by expensive soil Can be removed by expensive soil

cleaningcleaning– Reeds may be able to concentrate and so Reeds may be able to concentrate and so

remove them in their tissuesremove them in their tissues

Pollution - biotransformationPollution - biotransformation

Biotransformation is when organisms metabolise Biotransformation is when organisms metabolise chemicals into different chemicals. Typically chemicals into different chemicals. Typically this is a detoxification process.this is a detoxification process.

Sometimes less toxic chemicals are changed into Sometimes less toxic chemicals are changed into more toxic chemicalsmore toxic chemicals– e.g. – metallic mercury to very toxic methyl mercurye.g. – metallic mercury to very toxic methyl mercury– Minamata bay, JapanMinamata bay, Japan

Pollution - BiomagnificationPollution - Biomagnification

If a pollutant is not excreted or If a pollutant is not excreted or destroyed by an organism, it will destroyed by an organism, it will concentrate in the animal’s body.concentrate in the animal’s body.

If that animal is subsequently If that animal is subsequently consumed, all of the toxin will pass to consumed, all of the toxin will pass to the consumerthe consumer

Consequently, the consumer will have a Consequently, the consumer will have a higher concentration of toxin in their higher concentration of toxin in their body.body.

HCB = hexachlorbenzeneHCB = hexachlorbenzene

Correlation between DDE concentrations in the eggs of Alaskan falcons and hawks and reduction in the thickness of their eggshells (compared with shells collected prior to 1947). DDE is a metabolite of DDT. Data from T. J. Cade, et. al., Science 172:955, 1971.

Species LocationAverage

Concentrationof DDE in Eggs (ppm)

Reduction inShell

Thickness

Peregrine falconAlaskan tundra (north

slope)889 -21.7%

Peregrine falcon Central Alaska 673 -16.8%

Peregrine falcon Aleutian Islands 167 -7.5%

Rough-legged hawk

Alaskan tundra (north slope)

22.5 -3.3%

Gyrfalcon Seward Peninsular, Alaska 3.88 0

http://www.ourstolenfuture.org/Basics/chemlist.htm

Tributyl TinTributyl Tin

Anti fouling chemical (now banned) Anti fouling chemical (now banned) used to prevent build up on ship’s hullsused to prevent build up on ship’s hulls

In higher concentrations can lead to In higher concentrations can lead to changes in molluscs e.g. dog whelks/ changes in molluscs e.g. dog whelks/ oysters oysters – Sex ratio changes/ bifurcate penisSex ratio changes/ bifurcate penis

““Love Canal”Love Canal”– housing estate near Niagara falls, built on housing estate near Niagara falls, built on

chemical dump (dioxin, benzene)chemical dump (dioxin, benzene)– Low birth weight and growth retardationLow birth weight and growth retardation– CanalCanal