Human Impacts on the Climate

• Decreased pH of oceans:

  • Corals die as their calcium carbonate shells dissolve + damage to mollusc shells/ coral bleaching
• Coral bleaching - occurs when the water becomes too hot, coral expels the algae that live in its tissue, turning the coral bleach white.
• Possible changes to farming practices:

  • Rotating crops - reduce pests and mineral depletion
  • Salt-tolerant crops - overcome rising sea levels
  • Feeding cows high-sugar grasses - less cellulose = release less methane
  • Drought-resistant crops - tackle low and fluctuating water supply
  • improving drainage - aerate water-logged and anaerobic soils. Reinstate meadows
  • Keeping the soil healthy - using minimal preparation of land for growing crops (tillage)and cover crops like cover to protect and improve soils between crops
• Ammonification - Decomposers (saprotrophs) decay dead plants and animals, faeces, and urine into ammonium (NH4+)
• Nitrification - ammonium ions in the soil are converted into nitrites and then nitrates by nitrifying bacteria. Plants then absorb these nitrate ions.

  bacteria involved:

  • nitrosomonas- convert ammonium ions to nitrite ions
  • nitrobacter- convert nitrite ions to nitrate ions

  They are both aerobic, and so require oxygen for nitrification.
• Nitrogen fixation - nitrogen-fixing bacteria convert atmospheric nitrogen gas into ammonium ions

  bacteria:

  • Azotobacter - free living in soil
  • Rhizobium - found in root nodules of legumes
• Denitrification - denitrifying bacteria convert nitrates to nitrogen gas. Anaerobic conditions are required for this, such as waterlogged soil.
• To aid the nitrogen cycle:

  • Plough and drain soil to improve aeration. encourages nitrifying bacteria and discourages denitrification
  • Cultivation of legumes in the soil so rhizobium will carry out nitrogen-fixation in the plants. When the legumes die the nitrogenous compounds enter the soil to be broken down.
• Conservation methods:

  1. International cooperation - restricting trade or whaling
  2. Gene banks - sperm/ seed banks (helps to keep rare alleles)
  3. Legislation - laws protecting habitats and wildlife
  4. Ecotourism - aims to minimise the negative impacts of tourism by: Contributing to conservation, educating visitors, working with locals
  5. Protecting a particular area (e.g. Site of Special Scientific Interest (SSSI))
  6. Education - public awareness campaigns on endangered species
• When reintroducing species, scientists consider:

  • Habitat - make sure the receiving habitat it suitable, the effect on biodiversity or habitat of introduction of species
  • Research - Expertise on the animal, such as habitat, food, and breeding
  • Consultation - consult neighboring land owners and local stakeholders to make sure they don’t oppose reintroduction
  • Correct individuals - a suitable disease-free donor population is identified
• Re-introduction into areas with no well-establish population can help as:

  • fewer predators for the species
  • less intraspecific competition for food/nest sites/habitats
  • less likely to spread disease as fewer initial numbers
• Removal of hedgerows to make larger fields - this removes habitats, decreasing biodiversity. also removes wildlife corridors/ nest sites/breeding sites
• Monoculture - reduces biodiversity as only one species of insect can make habitats in the crops. roots also grow to the same length, extracting the same minerals from same depth, increasing use of inorganic fertilisers
• Overgrazing - when plants are exposed to intensive grazing for extended periods of time. leads to soil erosion and desertification. hooves of cattle compact soil, driving air out and preventing water drainage, anaerobic conditions for denitrification.
• Consequences of deforestation:

  • Climate Change - less co2 removes from atmosphere by photosynthesis. Felled trees also increase co2 levels as combustion of trees releases co2, saprophytes release co2, fossil fuels in transport
  • Destruction of Habitats - decreases biodiversity, this is bad as plants can be used for medicines and so could be lost and medicine not be produced
  • Soil Erosion - roots absorb water, stabilizing soil, without it soil isn’t stable. removal of topsoil, which contains highest conc of mineral ions, if washed into pond could result in eutrophication.
• Forest Management - sustainable replanting and regeneration of forests. It is possible to remove timber without destroying the forest ecosystem.
• Coppicing is a method where the tree trunk is cut to a stool a few centimeters high, allowing new shoots to emerge and grow into poles. Poles can be cut on rotation to produce different width of timber. After an area is coppiced, birds and insects move to a non-coppiced area.
• Selective Cutting is a method where some of the larger trees are felled while others are left in place, useful on steep slopes as total removal of trees would leave soil vulnerable to soil erosion. helps maintain nutrients in forest soil and minimise amount of soil washed away into rivers or other water
• Planting Trees at optimum distances apart reduces intraspecific competition which leads to trees growing tall and thin and so producing poor quality timber.
• Controlling Pests and Disease ensures trees grow well and produce good quality timber, meaning fewer trees have to be felled.
• Overfishing is a problem as increased intensity and efficiency of modern fishing in having a negative effect on the populations of marine ecosystems
• Effects of overfishing:

  • Drift nets can catch non-target species such as turtles or dolphins
  • Trawling damages the sea floor habitat of organisms such as molluscs
  • Can catch organisms that are the prey of other species, affecting whole food webs
• Controls on overfishing:

  • impose quotas so only certain mass of fish could be caught
  • ensure mesh size of nets are large enough to let young fish escape, ensure young fish can grow and become sexually mature to reproduce
  • exclusion zones so there cannot be any fishing during breeding season on the fishes breeding ground
• Fish farming is a form of aquaculture that involves the breeding and rearing of fish in enclosures in ponds, lakes, estuaries or in tanks on land.

  Advantages of farmed fish over traditional livestock :

  • convert food into protein more efficiently
  • greater proportion of fish body is edible
  • lower carbon footprint
• Fish farm problems:

  • diseases spread very fast because of high density. large amounts of antibiotics and pesticides have to be use, could potentially harm other organisms such as marine invertebrates
  • waste from fish farms can get into water around the fish pens and lead to eutrophication
  • PCBs and pesticides are more concentrated in farmed fish than wild fish (environmental toxins)
  • local environment can be damaged
• Planetary Boundaries - provide a safe operating space for humanity. Scientists believe that once human activity has passed certain thresholds, there is a risk of irreversible and abrupt environmental change.