The UN has described the world’s forests as
‘fundamental’ to human well-being and survival.
- Over 1.6 billion people depend on forests and over 90 per cent of these are the poorest in societies.
- Forests, like other ecosystems, are essential for human wellbeing through their ‘services’, as summarised in Table 6.1, as well as being the source of 80 per cent of global biodiversity.
- Deforestation affected an estimated 13 million hectares of forests per year between 2000 and 2010.
- However, net loss was reduced because of afforestation.
- Figure 6.5 (page 116) depicts a model often used in geographical studies: the environmental Kuznets curve.
- This suggests societies reach a tipping point where exploitation changes to more protection.
Factors affecting the timing of this attitudinal change are:
- the wealth of countries
- the rising knowledge of the role the environment plays in human well-being
- the aid given to poorer nations to help choices over exploitation
- the political systems and enforcement of environmental laws
- the participation of locals
- the power of TNCs.
the environmental Kuznets curve
Forests, like other ecosystems, are essential for human wellbeing through their ‘services’,
deforestation rates
- Between 1990 and 2015 the rate of net global deforestation slowed down by more than 50 per cent and total forest carbon emissions decreased by over 25 per cent according to the Food and Agriculture Organization of the UN (FAO).
- Increased sustainable management will hopefully result in greater reductions in carbon emissions from forests.
- Thirteen per cent of forests - 524 million hectares - are now classed as ‘conserved’.
- Brazil and the USA have the largest National Parks and Forest Reserves.
- Europe, North and Central America have large tracts that have been protected for over a century, with recent increases in Asia and Africa.
- Protective legislation has been combined with a greater involvement of local communities in planning and in developing policies, which is critical for long-term successful reductions in forest loss.
- Forest product extraction technology is improving, and carbon sequestration projects are increasing.
- However, such designation does not always mean conservation in practice.
Attitudes and players
Human well-being can be enhanced through a more sustainable interaction with ecosystems. The support of different players, especially governments and NGOs, is important. However, players may have different attitudes: economic, social, political and environmental.
Sustainable management:
The environmentally appropriate, socially beneficial and economically viable use of ecosystems for present and future generations.
Uk forest
- Following centuries of exploitation, forest cover in the UK had dropped from 80 to under ten per cent by the end of the nineteenth century.
- The Forestry Commission planted fast-growing exotic conifers such as Sitka Spruce on the moors of Wales, the Scottish Highlands and Lake District.
- Forest cover increased by 25 per cent between 1870 and 1947, and by 50 per cent between 1948 and 1995.
- By 2016, thirteen per cent of the UK was forested, with increasing numbers of indigenous species planted.
Impacts of rising temperatures
lobal warming is increasing temperatures globally, and since warmer air affects evaporation and stores more water, the amount of water in the atmosphere will increase. As a result, rain dropped during individual storms can increase, resulting in flash floods.
This specification requires you to know about the uncertainty of global projections and three specific implications for:
This specification requires you to know about the uncertainty of global projections and three specific implications for:
- precipitation patterns
- river regimes
- cryosphere and drainage basin water stores.
Key concept: The Arctic water cycle
The Arctic plays a large role in global climate as its sea ice regulates evaporation and precipitation. The Arctic carbon cycle is very sensitive to climate change, making future projections difficult.
the arctic p1
- Earth’s cryosphere has already been affected by global warming.
- Over the last twenty years the Antarctic and Greenland ice sheets have been losing mass; most glaciers have continued to shrink, and Arctic sea ice and northern hemisphere spring snow cover have continued to decrease in extent and thickness (Figure 6.6).
- The Arctic is an early warning system for the rest of the planet, acting as a barometer of the environmental impacts resulting from fossil fuel climate forcing.
- In the past few decades average Arctic temperatures have risen twice as fast as global averages: three to four degrees in Alaska and north-west Canada.
- They could soon rise another three to four degrees over land, and up to seven degrees over the oceans.
- There are huge implications for ocean currents, air circulation, sea level rise and flooding beyond the region.
- As a net sink, the Arctic stores far more carbon than any other region, with five to fourteen per cent of total oceanic stores, but it is also more vulnerable to global warming.
- Amplified atmospheric warming over the Arctic Ocean in autumn is already evident, with varying predicted effects as shown in Table 6.2.
the arctic p2
- In the short term an increase in CO, uptake is predicted, but with further sea-ice loss, increases in marine plants such as phytoplankton may cause a limited net increase in the uptake of CO, by Arctic surface waters.
- In the long term, a net outward flux of carbon is expected because of rivers bringing carbon from melted permafrost stores, and loss of methane hydrate from destabilised sea floor deposits stored for thousands of years.
- Carbon uptake by terrestrial plants is increasing because of longer growing seasons and also the slow northward migration of boreal forests.
- There is a high risk of irreversible feedback, called runaway global warming.
- Figure 6.10 on page 122 shows such feedback loops.
- There are two types of positive climate feedbacks in the Arctic from rising temperatures: sea-ice loss and carbon feedbacks.
Arctic barometer:
A barometer measures pressure. The Arctic is already showing pressure on its natural systems from anthropogenic influences.
Effects of global warming on the artic and beyond
Effects on the water cycle
- Warm water flowing into the Arctic from the Pacific and Atlantic
- Rising local air temperatures
- Shrinkage of sea ice; the Arctic ice cap averages only 3 m thick and melting is increasing faster than anticipated
- Run-off of fresh, cold water, which will alter marine ecosystems and the food chains dependent on the saline waters; this is predicted to affect areas outside the Arctic Ocean by 2100
- Funnelling of more cold water into the oceanic conveyer belt
Effects of global warming on the artic and beyond
Effect on carbon cycle
Increased or new emissions of:
* CH4 from destabilisation of wetlands and sea floor deposits containing methane hydrate, stored for thousands of years
* mainly CH4 and some CO2 from thawing permafrost
* CO2 from increased forest fires as boreal forests dry out; they may also absorb more CO2 and CH4 from the atmosphere
Loss of Arctic albedo
Albedo is a measure of how sunlight is reflected away from the Earth’s surface. Ice has a high reflectivity index, so a reduction in the amount of sea ice may create a positive feedback loop: melting allows more heat absorption, causing more melting.
Loss of reflective (cooling) albedo is from:
- less summer sea ice
- the replacement of (lighter) tundra with (darker) forests as they ‘advance’
north with improving temperatures from climate shift.
Black carbon (soot) pollution on snow adds to heat absorption and melting.
Carbon CO2 feedbacks
Carbon emissions will outpace uptake as warming continues:
- Increased CO, emissions from tundra soils.
- Forest growth will absorb more of the Sun’s energy, accelerating climate change.
- Methane hydrates are found in permafrost and ocean sediments in shallow water. They store more carbon than all of the proven reserves of coal, oil and natural gas together. However, they destabilise after thawing and will add to greenhouse gasses; CH, is 25 times more powerful a greenhouse gas than COz.
IPCC projections for the future: two extreme RCP scenarios
RCP 2.6 Strong mitigation (the 2 degree future)
Agreed at COP21 Paris 2015 by all countries
Mean temperature rise projected to be between
1.5°C and 2°C by the end of the twenty-first century
The average warming for land regions is 2.3 °C, compared to global average of 1.8 °C
Many regions will experience much greater (or lesser) increases in temperature; the Arctic is likely to have increases of about 8°C
by 2100
IPCC projections for the future: two extreme RCP scenarios
RCP 8.5 Business as usual
We continue to use fossil fuels with no mitigation (runaway global warming)
Emissions continue to rise, so global temperature is predicted to reach 5.6 °C
above the pre-industrial level by 21.00
Some regions are projected to warm by more than 15 °C
(e.g. the Arctic)
The impacts of such a scenario are likely to be large and costly
Key concept: Modelling
Scientists have to use models because of limited first-hand data. Supercomputers are used to fill in the gaps. Modelling suggests parts of the Arctic and Europe may experience greater precipitation as the Arctic transitions toward a seasonally ice-free state. Figure 6.7 shows the wide variations predicted by modelling in 2015.
Albedo flip:
When the sunlight reflected by white ice is suddenly absorbed as ice melts, creating a dark surface of open water.
Ocean health
The World Wide Fund for Nature (WWF), an international pressure group, warns that climate change is affecting ocean temperatures, the supply of nutrients, ocean chemistry, food chains, wind systems, ocean currents and extreme events such as cyclones. The changes may be categorised under: bleaching, acidification, rising sea levels and loss of sea ice. These changes then affect the distribution, abundance, breeding cycles and migrations of the marine plants and animals that millions of people directly or indirectly rely on for food and income.
Research, such as that carried out in the North Sea, suggests that marine organisms may be responding faster to climate change than terrestrial plants and animals, with some shifts of animals and some plants towards the poles to compensate for a warming environment.
The resulting changes to the marine food web from global warming pose threats for a large proportion of the planet one way or another. This applies to both natural oceanic ecosystems and aquaculture. The concept of forest ecosystem services, shown in Table 6.1 on page 115, may also be applied to oceans
