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Flashcards in Amazon and tundra Deck (40):
1

Amazon background

The Amazon rainforest in South America occupies an area of more than 6 million km2

  • The majority - 70% - of the rainforest is in Brazil, but the forest also extends into parts of 6 neighbouring countries (Peru, Ecuador, Venezuela, Colombia, Bolivia and Guyana)

2

Amazon climate (water cycle)

  • Its climatic features are
    • High average annual temperatures between 25℃ and 30℃
    • Small seasonal variation in temperature
    • High average annual rainfall (>2000 mm) with no dry season
  • High average annual temperatures are a response to intense insolation throughout the year, however significant cloud cover ensures that maximum temperatures do not reach the extremes of sub-tropical desert climates
  • Seasonal differences in temperature are small and convectional rain falls all year round, though most areas experience at least one drier period
    • Between 50 and 60% of precipitation in Amazonia is recycled by evapotranspiration

3

Amazon - key stores (water cycle)

  • Atmosphere
    • High temperatures allow the atmosphere to store large amounts of moisture (i.e. absolute humidity is high)
    • Relative humidity is also high
  • Soil/groundwater
    • Abundant rainfall and deep tropical soils lead to significant water storage in soils and aquifers
    • Rio Hamza flows from west to east (below the Amazon) from the Acre region under the Andes, through the Solimoes, Amazonas and Majaro basins before opening onto the Atlantic Ocean
      • 200km to 400km wide
      • 600 kilometres long
  • Vegetation
    • Rainforest trees play a crucial role in the water cycle, absorbing and storing water from the soil and releasing it through transpiration
  • Amazon River
    • 6,992 km long

4

Amazon - key flows (water cycle)

  • Precipitation
    • High annual rainfall in the Amazon of 2200mm
    • Evenly distributed precipitation throughout the year though a short drier season occurs in some places
    • High-intensity, convectional rainfall
    • Interception by forest trees is high (around 10% of all precipitation), and intercepted rainfall counts for 20-25% of all evaporation
  • Evapotranspiration
    • High rates of evaporation and transpiration due to high temperatures, abundant moisture and dense vegetation
    • Strong evapotranspiration-precipitation feedback loops sustain high rainfall totals
    • Around half of incoming rainfall is returned to the atmosphere by evapotranspiration
      • Most evaporation is from intercepted moisture from leaf surfaces
      • Moisture lost in transpiration is derived from the soil via tree roots
  • Runoff
    • Rapid runoff related to high rainfall, intensive rainfall events and well-drained soils
    • Depending on seasonal distribution of rainfall, river discharge may peak in one or two months of the year

5

Amazon climate background - how does the sun heat the earth?

  • Sun emits solar radiation
  • This can be absorbed by the Earth’s surface, causing it to warm up and warm the atmosphere above by conduction and convection
  • The Earth loses energy as long-wave radiation which can be absorbed by clouds or gases in the atmosphere
  • The hottest parts of the world receive the most solar radiation

6

Amazon climate background - why does solar radiation vary with latitude?

  • At the equator the Sun is directly overhead and thus more concentrated giving out solar radiation at 1 Kw/m2
    • Meanwhile at higher latitudes (60° N/S) the Sun’s energy is spread out due to the curvature of the Earth, leading to a lower ratio of solar radiation at ½ Kw/m2
  • At the poles, solar radiation has to pass through a greater amount of atmosphere due to the curvature of the Earth
    • This increases the potential for reflection and scattering in the Earth’s atmosphere, reducing solar radiation

7

Amazon climate background - the Tri Cellular Model

  • The unequal heating of the Earth by the Sun is what drives our weather
  • The atmosphere (and the oceans) move to equalise the differences between the energy received at the equator and the poles
  • In the atmosphere, at a macro scale, this equalisation process leads to major convection cells in the troposphere
  • There are three convection cells in each hemisphere:
    • Hadley cells (0-30°)
    • Ferrel cells (30-60°)
    • Polar cells (60-90°)

8

Amazon climate background - the ITCZ

  • The equator receives greater amounts if radiation and therefore heat
  • Heat from the Earth’s surface causes air above to warm and rise
  • Rising air creates a zone of low pressure on the surface around the equator
  • Air rises, expands and cools
  • As air cools it is not able to hold as much water vapour
  • Water condenses as clouds, particles collide until rain droplets form
  • Convectional rainfall falls in large quantities at the equator, making the growth of tropical rainforest possible

9

Amazon - how geology affects the water cycle

  • Impermeable catchments (e.g. large parts of the Amazon Basin are an ancient shield area comprising impermeable, crystalline rocks) have minimal water storage capacity resulting in rapid runoff
    • These are the Guiana and Brazil Shields
  • Permeable and porous rocks such as limestone and sandstone store rainwater and slow runoff as they allow infiltration

10

Amazon - how relief affects the water cycle

  • Most of the Amazon Basin comprises extensive lowlands
    • In areas of gentle relief water moves across the surface (overland flow) or horizontally through the soil (throughflow) to streams and rivers
  • In the west the Andes create steep catchments with rapid runoff
  • Widespread inundation across extensive floodplains (e.g. the Pantanal) occurs annually, storing water for several months and slowing its movement into rivers.

11

Amazon - how temperature affects the water cycle

  • High temperatures throughout the year generate high rates of evapotranspiration
  • Convection is strong, leading to high atmospheric humidity, the development of thunderstorm clouds and intense precipitation
  • Water is cycled continually between the land surface, forest trees and the atmosphere by evaporation, transpiration and precipitation

12

Impact of deforestation on the Amazon water cycle - theory

  • Deforestation has a huge impact on the water cycle and has the potential to change the climate at local and regional scales
    • Converting rainforest to grassland increases its runoff factor by 27, and half of all rain falling on grassland goes directly into rivers
    • Deforestation also increases soil erosion by a factor of 11
  • Rainforest trees are a crucial part of the water cycle, extracting moisture from the soil, intercepting rainfall and releasing it to the atmosphere through transpiration, as well as stabilising forest albedo and ground temperatures
    • This cycle sustains high atmospheric humidity which is responsible for cloud formation and heavy convectional rainfall
    • Deforestation breaks this cycle and can lead to permanent climate change
  • However, the impact of deforestation on water cycles is not just local
    • Projections of future deforestation in Amazonia predict a 20% decline in regional rainfall as the rainforest dries out and forest trees are gradually replaced by grassland
    • Nor is it just just deforested areas that experience a reduction in rainfall: disruption of the regional water cycle means that forests hundreds of kilometres downwind of degraded sites are affected too

 

  • Deforestation
    • Reduces rates of evapotranspiration
    • Greatly increases surface runoff and therefore water storage in the soil
    • Reduces rate of atmospheric transport
    • Makes flooding more likely as no interception occurs and soils will quickly become waterlogged

13

Impact of roads and hydroelectricity on the Amazon water cycle

  • Building of roads and infrastructure
    • Creates more impermeable surfaces, which increases surface runoff and decreases percolation of water into the soil and therefore groundwater storage
  • Hydroelectric power stations
    • Dams will increase rates of evaporation as large quantities of water will be stored in dams with large surface areas and limited protection from the sun

14

Impact of deforestation on the Amazon water cycle - Madeira basin

  • Deforestation in the Amazon has averaged around 17,500km2 per year between 1970 and 2013
    • As a result, 1/5 of the primary forest has been destroyed or degraded since 1970
  • In April 2014 devastating floods hit the Madeira river basin, the largest tributary of the Amazon (900,000 km)
    • At Porto Velho the river reached record levels of 19.68m above normal, causing the deaths of 60 people and the evacuation of 68,000 as well as outbreaks of cholera and leptospirosis
    • In total, 300,000 people were affected and a key road, the BR-264, was cut off, causing shortages of food and fuel supplies
  • In the Upper Madeira river basin human activity has modified stores and flows in the water cycle
    • Deforestation has reduced water storage in forest trees, soils (which have been eroded), permeable rocks (due to more rapid runoff) and in the atmosphere.
    • At the same time fewer trees mean less evapotranspiration and therefore less precipitation
    • Meanwhile, total runoff and runoff speeds have increased, raising flood risk throughout the basin.
  • Despite torrential rains in the upper basin of the Madeira River, the main driver of the flood was deforestation in Bolivia and Peru
    • Between 2000 and 2012, 30,000 km2 of Bolivian forest was cleared for subsistence farming and cattle ranching
    • Much of this deforestation took place on the lower slopes of the Andes resulting in massive reductions in water storage and increases in surface runoff exacerbated by the steep relief of the ground

15

Amazon - key stores (carbon cycle)

  • The Amazon rainforest is a major global reservoir of stored carbon
  • Vegetation
    • Amazonia’s humid equatorial climate creates ideal conditions for plant growth
      • Net primary productivity (NPP) is high, averaging 2500 grams/m2/year and the biomass is between 400 and 700 tonnes/ha
      • Large forest trees typically store around 180 tonnes C/ha above ground
      • Vegetation density is 75,000 trees per km2
    • 100 billion tonnes of carbon stored in the amazon’s 5.3 million sq km of forest trees
      • 60% of rainforest carbon stored in above ground biomass
      • This accounts for 17% of global terrestrial vegetation carbon stock
    • There are an estimated 390 billion trees made up of 16,000 species
      • However, 227 ‘hyperdominant’ species accounted for half of the Amazon’s trees
    • Home to 40,000 plant species
  • Peat Bogs
    • 90% of the Amazonian carbon stock is held in peat bogs
    • The Naranon basin in Peru contains 50% of the Peruvian Amazon’s carbon stock while being stored in only 3% of the land.
    • Extremely dense store of carbon
  • Roots
    • Rainforest trees typically store 40 tonnes C/ha below ground in their roots
    • Additionally, there are large networks of above ground roots in poor soil areas, for example in the Nauta area of the Amazon
  • Soil
    • Soil carbon stores average between 90 and 200 tonnes/ha
    • Amazonia’s leached and acidic soils contain only limited nutrient stores
      • The fact that such poor soils support a biome with the highest NPP and biomass of all terrestrial ecosystems, emphasises the speed with which organic matter is broken down, mineralised and recycled
  • Leaf litter
    • Leaf litter stores are extremely limited due to the humid conditions and high temperatures which cause rapid decomposition

16

Amazon - key flows (carbon cycle)

  • Compared to other forest ecosystems, exchanges of carbon between the atmosphere, biosphere are rapid
    • Warm, humid conditions ensure speedy decomposition of dead organic matter and the quick release of CO2
    • Meanwhile, rates of carbon fixation through photosynthesis are high
    • 2.4 Gt of CO2 absorbed per year, 1.7 Gt released
    • Net increase of 0.7 Gt of carbon stored in the Amazon each year makes it an increasingly significant sink

17

Amazon - how climate affects the carbon cycle

  • Perfect for high rates of photosynthesis and primary production
    • 25-30℃, 2000mm of rainfall per year and intense sunlight
    • Amazonia alone accounts for 15-25% of all NPP in terrestrial ecosystems

18

Amazon - how vegetation affects the carbon cycle

  • Forest trees dominate the biomass of the Amazon Basin and are the principle carbon store
    • In total approximately 100 Gt of carbon is locked up in the Amazon rainforest
  • Clearly extremely significant in the carbon cycle as the driver of the flux of carbon from the atmosphere to the biosphere by the fixing of carbon through photosynthesis

19

Amazon - how organic matter in the soil affects the carbon cycle

  • Leaf litter and other dead organic matter accumulates temporarily at the soil surface and within rainforest soils
  • High temperatures and humid conditions promote rapid decomposition of organic matter by bacteria, fungi and other soil organisms
  • Decomposition releases nutrients to the soil for immediate take-up by tree root systems, and emits CO2 which is returned to the atmosphere

20

Amazon - how the mineral composition of rocks affects the carbon cycle

  • The geology of the Amazon Basin is dominated by ancient igneous and metamorphic rocks
    • Carbonates are largely absent from the mineral composition of these rocks
  • However, in the western parts of the basin, close to the Andes, outcrops of limestone occur
    • In the context of the slow carbon cycle they are significant regional carbon stores as they are prone to being broken down by the chemical weathering of carbonic acids in rainfall by carbonation, leading to emission of CO2
  • There are also vast differences in vegetation levels because of geology - in northern Peru there are two distinct forests
    • The Pebas Formation has soils which is 15 times more fertile than the Nauta

21

Impact of deforestation on the Amazon carbon cycle

  • The biomass of trees represents around 60 percent of all the carbon in the ecosystem, above ground carbon biomass in the rainforest is as dense as 180 tonnes per hectare.
  • Deforestation exhausts this carbon biomass store
    • Croplands and pasture contain only small amounts of carbon in comparison with forest trees
    • Grasslands on former rainforest contain around 16.2 tonnes of carbon per hectare and areas used for soya cultivation contain inly 2.7 tonnes/ha
  • Deforestation also drastically reduces inputs of organic material to the soil
    • Soils, depleted of carbon and exposed to strong sunlight, are able to support fewer decomposer organisms, thus reducing the flow of carbon from the soil to the atmosphere
  • In tropical rainforests, the principal store of plant nutrients such as calcium, potassium and magnesium is the forest trees
    • Rainforest soils contain only a small reservoir of nutrients and the rainforest is only sustained by a rapid nutrient cycle
    • In this way, deforestation destroys the main nutrient store (forest trees), removing most of the nutrients from the ecosystem
    • Nutrients no longer taken up by root systems are washed out of soils by rainwater; and soils, without the protective cover of trees, are quickly eroded away and leached by runoff
    • Researchers found that phosphorus levels in deforested soil fell by 44% after 3 growing seasons

22

Amazon management strategies - theory

  • The degrading or outright destruction of large areas of Amazon rainforest is an issue of international as well as national concern
    • This is because deforestation has implications for global climate change
    • Brazil is committed to restoring 120,000 km2 of rainforest by 2030
  • Indigenous people have lived sustainably in the rainforest for thousands of years, maintaining the water balance, carbon cycle and the forest’s biodiversity
    • These people survived as hunter-gatherers and shifting cultivators
  • Modern strategies to manage the Amazon rainforest sustainably fall into three categories
    • Protection through legislation
    • Reforestation
    • Improving agricultural techniques

23

Amazon management strategies - legislation

  • Since 1998 the Brazilian government has legislated to protect areas of primary forest unaffected by commercial developments through ‘Amazon Regional Protected Areas’ (ARPA) that now cover an area twenty times the size of Belgium
    • In 2015 44% of the Brazilian Amazon was comprised of wildlife reserves, national parks and indigenous reserves where farming is banned
  • Large-scale conservation is so important as the forest has so many uses, many of which are linked to the Earth’s life support systems: carbon sequestration, fresh water delivery and conservation of species
  • ARPA protects 200,000 square miles of forest, protecting habitats, and biological diversity, stabilising land tenure and storing vast amounts of carbon
    • The direct protection of land through legislation means that primary forest remains as natural as possible, this has positive effects on both the water and carbon cycles.
  • By reducing deforestation carbon remains locked in the forest trees which also will be able to sequester more carbon from the atmosphere
    • Additionally the nutrient cycle will not be broken leading to the sapping of all nutrients from soils and ensuring continued biodiversity for the future
  • In 2009 the Surui (natives of Rondonia in the Amazon) were the first indigenous group in Amazonia to join the UN’s REDD scheme
    • In 2013, Natura, a large cosmetics TNC, purchased 120,000 tonnes of carbon credits from the Surui

24

Amazon management strategies - reforestation and afforestation

  • In areas where deforestation has taken place trees may be replanted to preserve the environment
    • These trees can act as a store of carbon and water and limit damage to soil through exposure and subsequent sapping of nutrients
  • The Brazilian government are aiming to plant 73 million trees in the Amazon by 2023
  • Several reforestation projects, sponsored by local authorities, NGOs and businesses are underway, but progress has been slow
  • One such example is the Parica project in Rondonia in the western Amazon
    • This sustainable scheme aims to develop a 1000 km2 commercial timber plantation on government-owned, deforested land
    • The plan is for 20 million fast-growing, tropical hardwood seedlings, planted on 4000 smallholdings, to mature over a period of 25 years
    • Financial assistance is given to smallholders for land preparation, planting and the maintenance of plots, while tree nurseries provide them with seedlings
    • Timber will be exported along the Amazon and its tributaries through Manaus or Porto Velho
  • Afforestation and reforestation will struggle to create a forest akin in terms of biodiversity to the original primary forest since they are largely monocultures
    • However they are sustainable and are able to sequester carbon in the trees and soil, reduce CO2 emissions from deforestation, re-establish water and carbon cycles and reduce runoff and the loss of nutrients from the soil
    • Secondary forest can also provide a buffer, protecting more fragile primary forest from logging
  • Also in Rondonia, the indigenous Surui people participate in a scheme that aims to protect primary rainforest on tribal lands from further illegal logging, and reforest areas degraded by deforestation in the past 40 years
    • The Surui plant seedlings bred in local nurseries in deforested areas around their villages
    • The native species planted are chosen to provide them with timber for construction, food crops and, through logging, a sustainable source of income
  • In the Amazon 25% of the forest has been damaged or destroyed, this cannot be restored unless reforestation takes place
  • External example of reforestation is the Three North Forest in China a project designed to increase northern chinese forest cover from 5 to 15%, protect primary forest and halt the expansion of the Gobi desert.
    • Project begun in 1978, uses 70 aircraft for aerial seeding, trees now cover 18% of North China, the world's largest artificial forest, however has in some cases had a negative effect on the water cycle as sudden tree growth can deplete groundwater for example in Minqin where falls of levels of up to 19m were recorded.

25

Amazon management strategies - improving agricultural techniques

  • Farming is the main cause of deforestation in the Amazon, it also lacks sustainability due to the low fertility of soils.
  • Permacultures are a holistic approach that simulates nature whilst yielding food and energy for local people, this approach has been implemented in the village of Estiron in the Amazon.
    • Infiltration basins collect mulch water and nutrients so that foods like plantains and cassava can be produced nearby. Banana circles are also built close to homes to allow the tipping of kitchen waste and ashes in the middle of these circles providing a slow release nutrient source.
    • Contour row cropping system used where nitrogen fixing tree species slow water is it flows down the hill and provide nutrients for the soils, preventing the sapping of soils.
    • In steeper areas swales and rotting logs are put down to control soil erosion and hold valuable nutrients.
  • Terra Patral (natural and synthetic)
    • 1500 years ago Amazonian tribe people mixed their soils with bones, charcoal and manure to form Terra Patral.
    • Today this soil is some of the most fertile in the world, covering 0.1-0.3% of the low forested Amazon.
    • It is a carbon negative strategy and therefore has the potential to curb greenhouse emissions.
    • A synthetic version of Terra Patral, Biochar can be synthesised which can be added to soils to provide a fertiliser that is far more stable than other alternatives.
    • Has been deemed “black gold agriculture”, a method that has huge potential in the future. Leaching is limited high concentrations of charcoal and microbial life while the carbons porosity brings better retention of organic matter and a method of slow release for nutrients.

26

Arctic Tundra background

  • The Arctic tundra occupies some 8 million km2 in northern canada, Alaska and Siberia
    • It extends from the northern edge of the boreal coniferous forest to the Arctic Ocean and its southern limit approximates the 10℃ July isotherm
  • Climatic conditions in the tundra are severe and become more extreme with latitude
    • For eight or nine months a year the tundra has a negative heat balance, with average monthly temperatures below freezing
    • As a result the ground is permanently frozen with only the top metre or so thawing during the Arctic summer

27

Arctic tundra - key flows and stores (water cycle)

  • Low precipitation (50-350mm) with most precipitation falling as snow
  • Small stores in the atmosphere owing to low temperatures which reduce humidity
  • Limited transpiration because of the spareness of the vegetation cover and short growing seasons
  • Low rates of evaporation as much of the Sun’s energy in the summer is expended melting snow so that ground temperatures remain low and inhibit convection. Also, surface and soil water are frozen for most of the year.
  • Limited groundwater and soil moisture stores. Permafrost is a barrier to infiltration, percolation, recharge and groundwater flow
  • Accumulation of snow and river/lake ice during the winter months. Melting of snow, river and lake ice, and the uppermost active layer of the permafrost in spring and early summer, results in a sharp increase in river flow
  • Extensive wetlands, ponds and lakes on the tundra during the summer. This temporary store of liquid water is due to permafrosts which impedes drainage

28

Tundra - how temperature affects the water cycle

  • Average temperatures are well below freezing for most of the year so that water is stored as ground ice in the permafrost layer
  • During the short summer the shallow active layer thaws and liquid water flows on the surface
    • Meltwater forms millions of pools and shallow lakes which stud the tundra landscape
    • Drainage is poor: water cannot infiltrate the soil because of the permafrost at depth
  • In winter, sub-zero temperatures prevent evapotranspiration
    • In summer some evapotranspiration occurs from standing water, saturated soils and vegetation
  • Humidity is low all year round and precipitation is sparse

29

Tundra - how rock permeability and relief affect the water cycle

  • Permeability is low owing to the permafrost and the crystalline rocks which dominate the geology of the tundra in Arctic and sub-Arctic Canada
  • The ancient rock surface which underlies the tundra has been reduced to a gently undulating plain by hundreds of millions of years of erosion and weathering
  • Minimal relief and chaotic glacial deposits impede drainage and contribute to waterlogging during the summer months

30

Tundra - carbon sink vs. carbon source

  • The permafrost is a vast carbon sink
    • Globally it is estimated to contain 1600 Gt of carbon
      • 50% of earth’s carbon that’s stored in below ground pools
    • The accumulation of carbon is due to low temperatures which slow decomposition of dead plant material
    • Overall, the amount of carbon in tundra soils is 5 times greater than in the above-ground biomass
  • The flux of carbon is concentrated in the summer months when the active layer thaws
    • Plants grow rapidly in the short summer - long hours of daylight allow them to flower and fruit within just a few weeks
    • Nonetheless, NPP is less than 200 grams/m2/year
    • Consequently the tundra biomass is small, ranging between 4 and 29 tonnes/ha depending on the density of vegetation cover
  • During the growing season tundra plants input carbon-rich litter to the soil
    • The activity of microorganisms increases, releasing CO2 to the atmosphere through respiration
  • However, CO2 (and methane (CH4)) emissions are not just confined to the summer
    • Even in winter, pockets of unfrozen soil and water in the permafrost act as sources of CO2 and CH4
    • Meanwhile snow cover may insulate microbial organisms and allow some decomposition despite the low temperatures
  • In the past the permafrost functioned as a carbon sink, but today global warming has raised concerns that it is becoming a carbon source
    • At the moment the evidence is unclear - while outputs of carbon from the permafrost have increased in recent decades, high temperatures have stimulated plant growth in the tundra and greater uptake of CO2
    • This in turn has increased the amount of plant litter entering store
    • It is possible therefore, that despite the warming Arctic climate, the carbon budget in the tundra today remains in balance

31

Tundra - key stores (carbon cycle)

  • Atmosphere - roughly 125Pg of carbon North of 60ON
  • Ocean - Arctic Ocean = 3% of earth's oceans, but accounts for 5-14% of the earth's ocean carbon uptake.
  • Land - Arctic tundra stores carbon in the soil, accounting for around 1627 Pg in northern permafrost regions, 5x the level above ground in the biomass
    • Boreal forests store carbon as plant material, sequestering around 1.3 Pg/year

32

Tundra - key flows (carbon cycle)

  • Photosynthesis - 0.3-0.6Pg C/yr and increases with increased temperatures
  • Respiration - 31-100Tg C/yr and increases with increased temperatures
  • Decomposition - 40-84Tg C/yr and increases with increased temperatures

33

Tundra - how temperature affects the carbon cycle

  • Accumulation of carbon due to low temperatures which slow decomposition of dead plant material
    • Most of this carbon has been locked away for at least the past 500,000 years
  • Carbon is mainly stored as partly decomposed plant which remains frozen in the permafrost

34

Tundra - how vegetation affects the carbon cycle

  • Low temperatures, the unavailability of liquid water for most of the year and parent rocks containing few nutrients limit plant growth
  • Thus the total carbon store of the biomass is relatively small
  • Averaged over the year, photosynthesis and NPP are low, with the growing season lasting for barely three months
  • However, there is some compensation for the short growing season in the long hours of daylight in summer

35

Tundra - how organic matter in the soil affects the carbon cycle

  • Low temperatures and waterlogging slow decomposition and respiration and the flow of CO2 to the atmosphere
  • However global warming has led to warmer soils and increased decomposition of plant litter increases nutrient availability which in turn stimulates plant growth in the tundra and increases uptake of CO2, this is estimated to have caused the loss of almost 2,000 grams of carbon per square meter in over 20 years

36

Tundra - how rock permeability and mineral composition affect the carbon cycle

  • Impermeability of the permafrost means that rock type and permeability is less influential on the carbon and water cycle than it would otherwise be
  • Parent rocks contain few nutrients which limits plant growth

37

The oil and gas industry in the tundra - background

  • The North Slope of Alaska, between the Brooks Range in the south and the Arctic Ocean in the north, is a vast wilderness of Arctic tundra
    • Oil and gas were discovered here at Prudhoe Bay in 1968
  • From the start the development of the oil and gas industries on the North Slope presented major challenges
    • A harsh climate with extreme cold and long periods of darkness in winter
    • Permafrost, and the melting of the active layer in summer
    • Remoteness and poor accessibility
    • A fragile wilderness of great ecological value
  • Despite the challenges, production went ahead, driven by high global energy prices and the US government’s policy to reduce dependence on oil imports
    • Massive fixed investments in pipelines, roads, oil production plants, gas processing facilities, power lines, power generators and gravel quarries were completed in the 1970s and 1980s
    • By the early 1990s, the North Slope accounted for nearly 25% of the USA’s domestic oil production
    • Today the proportion is 6% though Alaska remains an important oil and gas province
      • Decline in recent years reflects two things: high production costs on the the North Slope and the massive growth of the oil shale industry in the USA
  • Oil and gas exploitation on Alaska’s North Slope has had significant impacts on the permafrost and on local water and carbon cycles

38

Impact of oil and gas industry on the tundra water cycle

  • Melting and solifluction of the permafrost and snow cover has increased runoff and river discharge making flooding more likely
    • This means that in summer, wetlands, ponds and lakes have become more extensive, increasing evaporation
  • Strip mining of aggregates (sand and gravel) for construction creates artificial lakes which disrupt drainage and also expose the permafrost to further melting
  • Drainage networks are disrupted by road construction and seismic explosions used to prospect for oil and gas
  • Water abstracted from creeks and rivers for industrial use and for the building of ice roads in winter reduces localised runoff

39

Impact of oil and gas industry on the tundra water cycle

  • Permafrost, the major carbon store in the tundra, is highly sensitive to changes in the thermal balance
    • In any areas, this balance has been disrupted by the activities of oil and gas companies which have caused localised melting of the permafrost
  • Permafrost melting is associated with
    • Construction and operation of oil and gas installations, settlements and infrastructure diffusing heat directly to the environment
    • Dust deposition along roadsides creating darkened snow surfaces, thus increasing absorption of sunlight
    • Removal of the vegetation cover which insulates the permafrost
  • Permafrost melting releases CO2 and methane (CH4)
    • On the North Slope, estimated CO2 losses from the permafrost vary from 7 to 40 million tonnes/year
    • CH4 losses range from 24,000 to 114,000 tonnes/year
    • Gas flaring and oil spillages also input CO2 to the atmosphere
  • Other changes to the local carbon cycle are linked to industrial development
    • For example the  the destruction or degrading of tundra vegetation reduces photosynthesis and the uptake of CO2 from the atmosphere
    • The thawing of soil increases microbial activity, decomposition and emissions of CO2
    • Moreover, the slow-growing nature of tundra vegetation means that regeneration and recover from damage takes decades
  • There is the potential for a positive feedback cycle to be created in the carbon cycle
    • It is so vulnerable because it is an extremely low energy system

40

Tundra - management strategies

  • Insulated ice and gravel pads
    • Layers of coarse sand and gravel generally around 2m thick to insulate the underlying permafrost and stop it being exposed to higher temperatures
  • Buildings and pipelines elevated on piles
    • Allows growth of vegetation underneath
    • Animals able to migrate
  • Lateral drilling
    • Reduces sites needed for drilling, generally each platform can take up 20% more oil.
    • Therefore reduced permafrost melting etc.
  • Better computer software in hydrocarbon discovery
    • Reduces numbers of exploration wells
    • This means there is a reduction in the infrastructure needed to build these wells e.g. roads
  • Refrigerated supports
    • Stabilize the temperature of the permafrost, stopping it melting
  • Utilidors
    • Elevated above the ground and insulated therefore reducing melting
    • Used to carry the water supply, sewers and heating piped between buildings.