Succession

2. Succession • The non-seasonal, directional (time) change in community within a habitat • Unstable r-strategists stable K-strategists

4. 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.

5. 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.

6. As a result of Succession • Stability increases (r  K) • Diversity increases • 2 types: • Primary - from bare rock (Xerarch) • Secondary – from a disturbed habitat e.g. water course silting (Hydrarch) • 2 mechanisms: • Autogenic – changes are caused by the organisms themselves e.g. lichen • Allogenic - change is elicited by external agency e.g. climatic event, landslide, human intervention

7. Human Impact on Ecosystems • Man impacts environments for a number of reasons: • Food production – agriculture and wild harvest • Energy production • Pollution • Together these activities stress ecosystems • Stress leads to a reduction in species diversity • Populations sizes may increase (lack of interspecific competition)

9. Human Impact on Ecosystems – Food Production • “The battle to feed humanity is over. In the course of the 1970’s the world will experience starvation of tragic proportions – hundreds of millions of people will die.” – Paul Ehrlich, The Population time Bomb, 1968. We now have more food than ever before - Improved irrigation and farming methods - High yield crops - Fertilizers & pesticides What Cost?

10. Effects of Intensive food Production-Problems • Monoculture • growing a single species over a large area – trees/ food crops • Loss of habitat including increase in field size for efficiency • Reduces species diversity • Loss of nutrients – leaching due to soil erosion • Invasion of opportunistic weeds • Intensification of disease/ predation problems • Loss of soil structure due to inorganic fertilisers leads to topsoil erosion

11. Effects of Intensive food Production - Solutions • CHEMICALS • Herbicides (weedkillers, natural/ synthetic) • Pesticides (insecticides & fungicides natural/synthetic) • Fertilisers (NPK & organic) • DIFFICULTIES • Toxicity (to consumer & non target species) • Bioaccumulation through food chain (leading to toxicity) • Resistance requiring stronger chemicals • Persistence • Pollution (leaching/ runoff)

12. Examples - Fertilisers • Fertilisers (organic or NPK) • Eutrophication excessive nutrients into water (deoxygenation) • Nitrate in water – blue baby syndrome due to nitrite oxidation of haemoglobin • Cancer – not certain

13. Examples - Pesticides • Pesticides can be toxic to man and other species • DDT/DDE – synthetic oestrogen • thin egg shell - birds of prey • altered sex ratio (small penis, testicles • RATS, alligators, fish • Link to breast cancer • Fall in sperm counts (controversial - sex more often) • Organic farmers better sperm quality (Denmark)

14. Examples - Herbicides • Kill indiscriminately • Good & bad weeds killed • Loss of food/ habitat for variety of animals • Loss of food web diversity – unstable • Loss of useful insect etc. species • Loss of soil improving microbes/ animals • Possibly toxic

16. Increasing Energy Needs • Energy requirements have increased • Principally they have been met by polluting fossil fuels • This has lead to carbon dioxide emissions increasing substantially Carbon dioxide causes GLOBAL WARMING

19. Global Warming • Principally due to carbon dioxide (60%) • Other gases include • Methane (20%) • CFCs (14%) • Nitrogen Oxides (6%) • Ozone (upper atmosphere) (8%) • Carbon dioxide has increased by 31% during industrial revolution • Increase due to combustion, deforestation

20. Climate change solutions • Change of 0.6°C over last century • Projected rise 1.5 ° -4.5 ° C • Not all due to Carbon Dioxide, sunspot activity • Solutions • Reduce fossil fuel combustion • Switch to alternative fuel sources (renewable) Conserve forests Add iron to sea

33. Global Warming Problems • Coral bleaching • Loss of photosynthetic algae (zooxanthellae) from commensal relationship due to 1°C increase in sea temperature • Disease spread • Malaria possible in south britain • Loss of species’ niches • e.g. arctic species on cairngorms http://www.metoffice.gov.uk/research/hadleycentre/models/modeldata.html

34. Food production needs to double to meet the needs of an additional 3 billion people in the next 30 years Climate change is projected to decrease agricultural productivity in the tropics and sub-tropics for almost any amount of warming

35. Other Pollution from combustion of fossil fuels • Acid rain (SO2, Nox) • Other pollutants • PM 10s - Asthma • Ozone layer • CFCs activated by high energy photons • Chlorine free radicals react with ozone in upper atmosphere

36. Pollution • Heavy metals • Interfere with enzyme action/ biochemical processes • Result of industrial activity, common at foundry sites/ gas works • Can be removed by expensive soil cleaning • Reeds may be able to concentrate and so remove them in their tissues

39. Pollution - biotransformation • Biotransformation is when organisms metabolise chemicals into different chemicals. Typically this is a detoxification process. • Sometimes less toxic chemicals are changed into more toxic chemicals • e.g. – metallic mercury to very toxic methyl mercury • Minamata bay, Japan

40. Pollution - Biomagnification • If a pollutant is not excreted or destroyed by an organism, it will concentrate in the animal’s body. • If that animal is subsequently consumed, all of the toxin will pass to the consumer • Consequently, the consumer will have a higher concentration of toxin in their body. • HCB = hexachlorbenzene

41. 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 Location Average Concentrationof DDE in Eggs (ppm) Reduction inShell Thickness Peregrine falcon Alaskan 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

42. Tributyl Tin • Anti fouling chemical (now banned) used to prevent build up on ship’s hulls • In higher concentrations can lead to changes in molluscs e.g. dog whelks/ oysters • Sex ratio changes/ bifurcate penis

43. “Love Canal” • housing estate near Niagara falls, built on chemical dump (dioxin, benzene) • Low birth weight and growth retardation • Canal