Human activity on Carbon and Water cycles Flashcards
(13 cards)
Growing resource demands
The biosphere sequesters about one quarter of fossil fuel carbon emissions every year, slowing down the rate of global warming
However, the biosphere’s capacity to sequester carbon dioxide is being reduced due to land conversion
Land conversion is being driven by an increasing demand for food, fuel and other resources
Deforestation and farming
Forests cover 30% of the Earth’s land area and absorb rainfall and increase groundwater storage
Deforestation occurs for either the timber or the space they occupy and is driven by the increasing demand for commodity production
An estimated 10 million hectares are deforested every year
Animals release Co2 and Methane when they respire and digest food
Deforestation impacts on the water cycle
Reduced interception by vegetation so infiltration to soil and groundwater changes
Increased erosion and surface run-off, increasing sediment eroded and transported into rivers
Deforestation impacts on the carbon cycle
Reduced storage in soil and biomass
Reduced carbon dioxide intake during photosynthesis
Increased carbon influx to atmosphere by burning and decomposing vegetation
Afforestation
Afforestation and reforestation are beneficial for carbon dioxide sequestration but can be controversial in its impacts:
- Commercial trees such as palm oil often store less carbon, use more water and are prone to disease
Grassland conversion
There are two main types of grassland which cover 26% of the Earth’s land area
Temperate grassland - no trees and a seasonal growth pattern linked to a large annual temperature range e.g. North America
Tropical grassland or Savannah- scattered trees with a wet and dry season e.g. Africa’s serengeti
Grassland conversion impacts on the carbon and water cycle
When grasslands are used too intensively for animals or agriculture it disrupts the carbon and water cycles
Rapid increase in population and changes from nomadic to sedentary farming along with the impacts of climate change and poor land management
Soil and ecosystem degradation is now becoming a worldwide issue which is leading to a loss in carbon storage
Impermeable surfaces build up and increase runoff and reduce evapotranspiration
Ocean acidification
due to their increasing uptake of carbon dioxide from the atmosphere, their overall pH is decreasing leading to ocean acidification
The acidity of the ocean today is estimated to be on average about 25% greater than it was during pre-industrial times
2015 = 8.1PH
19th century = 8.2PH
Coral reefs stop growing when PH = 7.8 or below
Ocean acidification increases the risk of marine ecosystems reaching a critical threshold of permanent damage
Ecosystem resilience is important - if the rate of acidification is slow enough, the organisms may be able to adapt to the changes and be more resilient
The Arctic Ocean is likely to be affected first due to its low pH threatening its ‘cold’ corals
Globally, coral reefs are already experiencing bleaching from increasing temperatures = marine algae give the bright colours and cannot survive in warmer temperatures
Removes carbonate ions and calcium carbonate which sea creatures need to form their shells and makes corals thinner
Causes of ocean acidification
Ocean acidification will be exacerbated by other factors including warming temperatures, tropical storms and pollution
How are marine organisms affected by ocean acidification
Reduced carbonate ions = animals use more energy building shells
Leads to thinner more fragile shells
More acidic water = the more it dissolves carbonate shells
This weakens the shells and allows attack via bio-erosion by molluscs worms and sponges
Major functions such as reef building may collapse leading to irreversible changes
Global warming is affecting ocean temperatures and currents as well as the supply of nutrients and marine food chains
These changes can be categorised under the following:
Bleaching
Acidification
Rising sea levels
Loss of sea ice
These changes then have an impact on distribution, abundance, breeding cycles and migration of marine plants and animals which millions of people depend on either directly or indirectly for food and income
Research suggests that marine organisms may be responding faster to climate change than terrestrial organisms
Importance of ocean health
All countries eat and either sell or buy fish
Fish is essential in developing countries
Coral reefs provide protection to coastal areas from waves (Hawaii)
Countries benefit from tourism - coral reefs (Great Barrier Reef)
Countries rely on exports of fish
Small scale fishing families rely on seafood for income and food
The FAO estimates that fishing supports 500million people and 90% are in developing countries
How are water stores affected?
Precipitation patters - drought and heavy rainfall
River regimes - in glacial areas, periods of snow melt increases the volume of meltwater feeding into rivers = increase in likelihood of flooding
Freshwater stores = glacial snow melt will decrease the amount of water stored in the cryosphere - drier regions will see a reduction in lake size and also ground water storage
