human impacts

• Carbon Cycle:

  • Carbon is a major component of all organic molecules
  • During the day, plants convert carbon dioxide into complex organic molecules during photosynthesis
  • Living organisms return carbon dioxide into the air during respiration
• Effects of human activities on the carbon cycle:

  • Deforestation increases the carbon dioxide content in the atmosphere
  • Land replaced by crops stores less carbon dioxide and when crops die, decomposers release carbon dioxide
  • Land replaced with cattle produces high levels of carbon dioxide and methane
  • Human activities have resulted in global and regional climate patterns changing due to the rise in atmospheric carbon dioxide levels and other greenhouse gases
• Consequences of global warming and climate change:

  • Increased frequency of extreme weather conditions
  • Polar ice caps melting
  • Increased frequency of forest fires
  • Changes in species distribution and biodiversity
  • Increased crop yields in some regions, but also increased pest populations
• Nitrogen Cycle:

  • Plants and animals cannot use atmospheric nitrogen
  • Nitrogen enters the food chains when plants absorb ammonium or nitrate ions through their roots
  • Key processes: Ammonification, Nitrification, Nitrogen fixation, Assimilation, Denitrification
• Key processes in the Nitrogen Cycle:

  • Ammonification: Decomposers decay dead plants and animals into ammonium ions
  • Nitrification: Ammonium ions are converted into nitrites and then nitrates by nitrifying bacteria
  • Nitrogen fixation: Nitrogen-fixing bacteria fix nitrogen gas into ammonium ions
  • Assimilation: Formation of organic nitrogen compounds
  • Denitrification: Denitrifying bacteria convert nitrate into nitrogen gas
• Human activities to aid the Nitrogen Cycle:

  • Ploughing and drainage of soil to improve aeration
  • Cultivation of legumes to carry out nitrogen fixation
  • Application of artificial fertilisers and manure to soil
• Eutrophication:

  • Fertilisers contain nitrates, potassium, and phosphate
  • High nitrate levels in waterways can be overcome by restricting fertiliser use and digging drainage ditches
• Endangered species:

  • Extinction is a natural process, but scientists are worried due to human influence
  • Main threats: Natural selection, non-contiguous populations, loss of habitat, overhunting, competition from other species, pollution
• Conservation techniques:

  • Protecting habitats from urban development
  • Gene banks for conservation of gene pools
  • International cooperation to restrict trade in endangered species
  • Education through public awareness campaigns
  • Ecotourism to minimize negative impacts of tourism
  • Legislation to protect habitats and wildlife
• National & international laws protect habitats and wildlife e.g. EU habitats directive prevents overfishing by imposing fishing quotas and preventing overgrazing
• Conservation of existing gene pools is important because:

  • Each species is a unique combination of genes and alleles, making them valuable
  • Breeds of animals and plants used in agriculture and horticulture may lack rare alleles that could be important in the future
  • Wild plants and animals can act as a gene bank for these alleles which can be bred with animals and crop plants
  • A large, varied gene pool increases the chance of a species surviving environmental change
  • Plants and animals may have the potential to help in the development of new drugs or medical treatments
• Reintroduction of species aims to re-establish a viable population of a species within its native habitat and can be a positive conservation strategy
• Agricultural exploitation has led to conflicts between agricultural production and conservation, with changes like:

  • Removal of hedgerows to make larger fields
  • Monoculture leading to reduced biodiversity and nutrient concentrations in the soil
  • Overgrazing causing soil erosion and desertification
• Deforestation is the removal of trees for various reasons like demand for timber, fuel, paper, farming, and infrastructure, leading to consequences like global climate change and habitat destruction
• Soil erosion occurs when topsoil, containing valuable nutrients, is removed, leading to issues like lowland flooding and decreased soil fertility
• Managed forests involve sustainable replanting and regeneration techniques like selective cutting, long rotation times, planting trees at optimum distances, controlling pests and diseases, and coppicing to preserve habitats and biodiversity
• Overfishing negatively impacts marine populations and ecosystems, with effects like reduced breeding populations, bycatch of non target species, and damage to sea floor habitats
• Fish farming can help overcome overfishing but can cause issues like diseased fish, pollution, resource use inefficiency, and environmental toxin contamination
• Farmed fish can eat a large amount of food, often other fish, which is inefficient
• Environmental toxins like PCBs and pesticides are more concentrated in farmed fish than in wild fish
• Local environment can be damaged by industries like the shrimp industry, leading to salinisation of soil and groundwater and destruction of mangroves
• Planetary boundaries define a 'safe operating space for humanity' and indicate that human activity has become the main driver of global environmental change since the Industrial Revolution
• There are 9 earth system processes with boundaries that mark the safe zone of the planet, some of which have already been crossed due to human activities
• The biodiversity boundary has been crossed, leading to extinction of species and reduced biodiversity in regions like tundra and marine environments
• The climate change boundary has been crossed, causing an increase in global temperature, climate change, and rise in sea levels
• The nitrogen boundary has been crossed due to denitrification from waterlogged soils and use of agricultural fertilisers leading to eutrophication
• The land use boundary has been crossed due to deforestation for farming and urban development, conflicting with the need to protect natural habitats
• The fresh water boundary is at risk due to changing landscapes, agriculture, increased human demand, water pollution, and climate change
• The chemical pollution boundary includes organic pollutants, radioactive materials, nanomaterials, and micro-plastics that can interact and produce harmful effects
• The ocean acidification boundary is avoidable and caused by decreasing pH due to dissolving carbon dioxide, affecting marine life like molluscs, corals, and fish
• The aerosol boundary is unquantified and includes microscopic particles in the atmosphere that can lead to respiratory problems and affect climate
• The ozone boundary has been avoided by banning substances like CFCs that caused ozone layer depletion
• Countries with a high GDP derived from natural resources may perceive environmental problems as less impactful to maintain prosperity
• Wealthier countries tend to be more concerned about environmental problems, but there are exceptions where less wealthy countries prioritize environmental issues
• Education and awareness measures are needed in countries where planetary boundaries were underestimated to inform students about environmental problems
• Exceeding the climate change planetary boundary could cause the loss of coastal habitats due to rising sea levels