Earths Life support systems Flashcards
(142 cards)
1
Q
How is water important in supporting life?
A
- Water provides a medium that allows organic molecules to mix and form more complex structures.
- Water helps to create benign thermal conditions on Earth. For example, oceans (occupy 71% of Earth’s surface) moderate temperatures by absorbing heat, storing it and releasing it slowly.
- Clouds made up of tiny water droplets and ice crystals reflect a fifth of incoming solar radiation and lower surface temperatures.
- Water vapour absorbs long-wave radiation from the Earth helping to maintain average global temperatures.
2
Q
What enables water to exist in liquid form on Earth?
A
The ubiquity of liquid water on Earth is due to the distance of the Earth from the Sun: it lies in the ‘Goldilocks zone’, which is perfect for water to exist in liquid form.
3
Q
How is water used for flora, fauna and people?
A
- Water makes up 65-95% of all living organisms and is crucial to their growth, reproduction and other metabolic functions.
- Plants need water for photosynthesis, respiration and transpiration
- Plants also require water to maintain rigidity and to transport mineral nutrients from the soil.
- In people and animals, water is the medium for all chemical reactions in the body including the circulation of oxygen and nutrients
- Transpiration of water from leaf surfaces by evaporation cools plants.
- Sweating is the cooling process in humans
- Water is also used to generate electricity, irrigate crops, provide recreational facilities and satisfy public demand. It is also used in food manufacturing, brewing, paper making and steel making.
4
Q
How is carbon important for life on Earth?
A
- Large molecules of carbon atoms such as proteins, carbohydrates and nucleic acids are essential in life
- Fossil fuels such as coal, oil and natural gas power the global economy.
- Oil is also used as a raw material in the manufacture of products ranging from plastics to paint and synthetic fabrics.
- Agricultural crops and forest trees also store large amounts of carbon available for human use as food, timber, paper, textiles and many other products.
5
Q
On a global scale, in what system do carbon and water flow?
A
In a closed system
6
Q
What areas do carbon and water flow between?
A
The atmosphere, oceans, land, and biosphere
7
Q
How long does the cycling of water and carbon take?
A
Days to millions of years
8
Q
At the macro-scale, what three stores does the global water cycle consist of?
A
The atmosphere, oceans and land
9
Q
By what processes does water move between stores?
A
Precipitation, evapotranspiration, run-off and groundwater flow
10
Q
How much carbon does long-term storage in sedimentary rocks hold?
A
99.9% of carbon on Earth
11
Q
What are he main pathways that carbon takes when it moves between stores?
A
Photosynthesis, respiration, oxidation (decomposition and combustion) and weathering
12
Q
What are systems?
A
Systems are groups of objects and the relationships that bind the objects together
13
Q
Define closed system
A
A system in which only energy can cross boundaries of the global water cycle and carbon cycle.
14
Q
What are open systems?
A
Where materials as well as the Sun’s energy cross system boundaries. Happens at smaller scales, e.g. drainage basin or forest ecosystem
15
Q
What is a reservoir?
A
A lake that stores water for human use.
16
Q
How much water do the oceans contain?
A
1,370,000 km cubed * 10cubed
17
Q
What percentage of global water is in the oceans?
A
97%`
18
Q
How much water does polar ice and glaciers contain?
A
29,000 km cubed * 10 cubed
19
Q
What percentage of global water is in polar ice and glaciers?
A
2%
20
Q
How much water does groundwater (aquifers) contain?
A
9,500 km cubed * 10 cubed
21
Q
What percentage of global water is in groundwater?
A
0.7%
22
Q
How much water do lakes contain?
A
125
23
Q
What percentage of global water is in lakes?
A
0.01%
24
Q
How much water do soils contain?
A
65
25
What percentage of global water is in soils?
0.005%
26
How much water does the atmosphere contain?
13
27
What percentage of global water is in the atmosphere?
0.001
28
How much water do rivers contain?
1.7
29
What percentage of global water is in rivers?
0.0001%
30
How much water does the biosphere contain?
0.6
31
What percentage of global water is in the biosphere?
0.00004%
32
According to the US Geological Survey (USGS), how much water does the global water cycle circulate every year?
Estimated 505,000 km cubed of water is circulated in a year
33
Describe the inputs and outputs of water
- Inputs of water to the atmosphere include water vapour evaporated from the oceans, soils, lakes and rivers, and vapour transpired through the leaves of plants. Together these processes are known as evapotranspiration.
- Moisture leaves the atmosphere as precipitation (i.e. rain, snow, hail, etc.) and condensation (e.g. fog). Ice sheets, glaciers and snowfields release water by ablation (melting and sublimation)
- Precipitation and meltwater drain from the land surface as run-off into rivers. Most rivers flow to the oceans through some, in continental drylands like southwest USA, drain to inland basins. A large part of water falling as precipitation on the land reaches rivers only after infiltrating and flowing through the soil.
- After infiltrating the soil, water under gravity may percolate into permeable rocks or aquifers. This groundwater eventually reaches the surface as springs or seepage and contributes to run-off.
34
What are the stores of carbon?
- The Atmosphere
- The oceans
- Carbonate rocks
- Fossil fuels
- Plants
- Soils
35
How much carbon does the atmosphere store?
600 billion tonnes
36
How much carbon do the oceans store?
38,700 billion tonnes
37
How much carbon do sedimentary rocks store?
60,000-100,000,000 billion tonnes
38
How much carbon do sea floor sediments store?
6,000 billion tonnes
39
How much carbon do fossil fuels store?
4,130 billion tonnes
40
How much carbon do land plants store?
560 billion tonnes
41
How much carbon do soils/peat store?
2,300 billion tonnes
42
What are the two strands of the carbon cycle?
The slow cycle and the fast cycle.
43
How does carbon stored in oceans operate in the slow carbon cycle?
- Carbon stored in rocks, sea-floor sediments and fossil fuels is locked away for millions of years.
- The total amount of carbon circulated by this cycle is between ten and 100 million tonnes a year.
- Carbon dioxide diffuses from the atmosphere into the oceans where marine organisms, such as clams and corals, make their shells and skeletons by fixing dissolved carbon together with calcium to form calcium carbonate. On death, the remains of these organisms sink to the ocean floor. There they accumulate and over millions of years, heat and pressure convert them to carbon-rich sedimentary rocks.
44
What role do sedimentary rocks have in the slow carbon cycle?
- Typical residence times for carbon held in rocks are around 150 million years,
- Some carbon-rich sedimentary rocks, subducted into the upper mantle at tectonic plate boundaries, are vented to the atmosphere in volcanic eruptions. Other exposed at or near the surface by erosion and tectonic movements are attacked by chemical weathering.
45
What role does chemical weathering have on the slow carbon cycle?
Chemical weathering processes such as carbonation are the result of precipitation charged with carbon dioxide from the atmosphere, which forms a weak acid. The acid attacks carbonate minerals in rocks, releasing carbon dioxide to the atmosphere, and in dissolved form to streams, rivers and oceans.
46
What role does partly decomposed organic material have on the slow carbon cycle?
On land, partly decomposed organic material may be buried beneath younger sediments to form carbonaceous rocks such as coal, lignite, oil and natural gas. Like deep-ocean sediments, these fossil fuels act as carbon sinks that endure for millions of years.
47
How much faster in the fast carbon cycle than the slow carbon cycle
Carbon circulates most rapidly between the atmosphere, the oceans, living organisms (biosphere) and soils. These transfers are between 10 and 1000 times faster than those in the slow carbon cycle.
48
What role do phytoplankton play in the fast carbon cycle?
- Land plants and microscopic phytoplankton in the oceans are the key components of the fast cycle.
- Through photosynthesis they absorb carbon dioxide from the atmosphere and combine it with water to make carbohydrates.
49
Describe respiration in the fast carbon cycle
Respiration by plants and animals is the opposite process and results in the release of carbon dioxide
50
Describe decomposition in the fast carbon cycl
Decomposition of dead organic material by microbial activity also returns carbon dioxide to the atmosphere.
51
Describe the carbon exchange between the atmosphere and the oceans in the fast carbon cycle.
- Carbon exchange also takes place between the atmosphere and the oceans.
- Atmospheric carbon dioxide dissolves in ocean surface waters while the oceans ventilate carbon dioxide back to the atmosphere.
- Through this exchange individual carbon atoms are stored (by natural sequestration) in the oceans for, on average, about 350 years.
52
What is the water balance equation?
Precipitation (P) = Evapotranspiration (E) + Streamflow (Q) +/- Storage
53
What does the water balance state?
The water balance equation summarises the flows of water in a drainage basin over time. It states that precipitation is equal to evapotranspiration and streamflow, plus or minus water entering or leaving storage.
54
What are the flows of the water cycle?
The principal flows in the water cycle that link the various stores are: precipitation, evaporation, transpiration, run-off, infiltration, percolation and throughflow.
55
What is precipitation?
Precipitation is water and ice that falls from clouds towards the ground. It takes several forms: most commonly rain and snow, but also hail, sleet and drizzle.
Precipitation forms when vapour in the atmosphere cools to its dew point and condenses into tiny water droplets or ice particles to form clouds. Eventually these droplets or ice particles aggregate, reach a critical size and leave the cloud as precipitation.
56
How can precipitation vary, and how does this affect the water drainage basin?
- Most rain on reaching the ground flows quickly into streams and rivers. But in high latitudes, and mountainous catchments, precipitation often falls as snow and may remain on the ground for several months. Thus there may be a considerable time lag between snowfall and run-off.
- Intensity is th amount of precipitation falling in a given time. High-intensity precipitation (e.g. 10-15 mm/hour) moves rapidly overland into streams and rivers.
- Duration is the length of time that a precipitation event lasts. prolonged events, linked to depressions and frontal systems, may deposit exceptional amounts of precipitation and cause river flooding.
- In some parts of the world (e.g. East Africa, Mediterranean) precipitation is concentrated in a rainy season. During this season river discharge is high and flooding is common. In the dry season rivers may cease to flow altogether.
57
What is transpiration?
Transpiration is the diffusion of water vapour to the atmosphere from the leaf pores (stomata) of plants. It is responsible for around 10% of moisture in the atmosphere. Like evaporation, transpiration is influenced by temperature and wind speed. it is also influenced by water availability to plants. For example, deciduous trees shed their leaves in climates with either dry or cold seasons to reduce moisture loss through transpiration.
58
What is condensation?
Condensation is the phase change of vapour to liquid water. It occurs when air is cooled to its dew point. At this critical temperature air becomes saturated with vapour resulting in condensation. Clouds form through condensation in the atmosphere.
59
Describe cumuliform clouds
- Flat bases and considerable vertical development
- Most often form when air is heated locally through contact with the Earth's surface. This causes heated air parcels to rise freely through the atmosphere (convection), expand (due to the fall in pressure with altitude) and cool.
- As cooling reaches the dew point, condensation begins and clouds form.
60
Describe stratiform clouds
- Develop where an air mass moves horizontally across a cooler surface (often the ocean).
- This process, together with some mixing with turbulence, is known as advection.
61
Describe wispy, cirrus clouds
- Form at high altitude
- Consist of tiny ice crystals
- Unlike cumuliform and stratiform clouds they do not produce precipitation and therefore have little influence on the water cycle.
62
What does condensation near the ground produce?
Produces dew and fog. Both types of condensation deposit large amounts of moisture on vegetation and other surfaces.
63
What are clouds?
Clouds are visible aggregates of water or ice or both that float in the free air
64
How do clouds form?
Clouds form when water vapour is cooled to its dew point
65
When does cooling occur?
- Air warmed by contact with the ground or sea surface, rises freely through the atmosphere. As the air rises and pressure falls it cools by expansion (adiabatic expansion). This vertical movement of air is known as convection.
- Air masses move horizontally across a relatively cooler surface - a process known as advection.
- Air masses rise as they cross a mountain barrier or as turbulence forces their ascent.
- A relatively warm air mass mixes with a cooler one.
66
What are lapse rates?
Lapse rates describe the vertical distribution of temperature in the lower atmosphere, and the temperature changes that occur within an air parcel as it rises vertically away from the ground.
67
What are the three types of lapse rates?
- Environmental lapse rate (ELR)
- Dry adiabatic lapse rate (DALR)
- Saturated adiabatic lapse rate (SALR)
68
Describe the ELR
The ELR is the vertical temperature profile of the lower atmosphere at any given time. On average the temperature falls by 6.5 degrees Celsius for every kilometre of height gained.
69
Describe the DALR
The DALR is the rate at which a parcel of dry air (i.e less than 100% humidity so that condensation is not taking place) cools. Cooling, caused by adiabatic expansion, is approximately 10 degrees celsius/km
70
Describe the SALR
The SALR is the rate at which a saturated parcel of air (i.e one in which condensation is occurring) cools as it rises through the atmosphere. Because condensation releases latent heat, the SALR, at around 7 degrees celsius/km, is lower than the DALR.
71
What is the evaporation?
- Evaporation is the phase change of liquid water to vapour and is the main pathway by which water enters the atmosphere.
- Heat is needed to bring about evaporation and break the molecular bonds of water.
- But this energy input does not produce a rise of temperature in the water. Instead the energy is absorbed as latent heat and released later in condensation. This process allows huge quantities of heat to be transferred around the planet; from the oceans to the continents; and from the tropics to the poles.
72
What is interception?
- Vegetation intercepts a proportion of precipitation, storing it temporarily on branches, leaves and stems.
- Eventually, this moisture either evaporates (interception loss) or falls to the ground.
- Rainwater that is briefly intercepted before dripping to the ground is known as throughfall.
- During periods of prolonged or intense rainfall, intercepted rainwater may flow to the ground along branches and stems as stemflow.
73
What happens to rainwater which falls to the ground and doesn't enter storage?
It follows the infiltration flowpath or overland flow into the rivers and streams.
74
What is infiltration?
Infiltration by gravity into the soil and lateral movement or throughflow to stream and river channels.
75
What is overland flow?
Overland flow across the ground surface either as a sheet or as trickles and rivulets to stream and river channels.
76
What are some ways in which interception loss is affected by?
- Interception storage capacity
- Wind speed
- Vegetation type
- Tree species
77
Describe interception storage capacity
Before the onset of rainfall, vegetation surfaces are dry and their ability to retain water is at a maximum. Initially most rainfall is intercepted. However, as vegetation becomes saturated, output of water through stemflow and throughfall increases. Interception therefore depends on the duration and intensity of a rainfall event.
78
Define wind speed
Rates of evaporation increase with wind speed. Turbulence also increases with wind speed causing additional throughfall.
79
How does vegetation type affect interception loss?
Interception losses are greater from grasses than from agricultural crops. Trees, which have a large surface area and aerodynamic roughness, have higher interception losses than grasses.
80
How do tree species affect interception loss?
Interception losses are far greater from evergreen conifers (e.g. spruce, pine) than from broadleaved, deciduous trees (e.g. oak, ash). This is because most conifers have leaves all year round, and water adheres to the spaces between conifer needles (like water on a comb). This increases evaporation.
81
When does overland flow occur?
It only occurs when soil become saturated and the water table rises to the surface. This process is known as saturated overland flow.
82
Where soils are underlain by permeable rocks, what path does water take?
Water seeps or percolates deep underground
83
What happens to the water after it has percolated?
The water then migrates slowly through the rock pores and joints as groundwater flow, eventually emerging at the surface as springs and seepages.
84
What happens to the water table by late October?
By late October, the water table is beginning to rise as temperatures and evapotranspiration fall. This recharge continues until late January.
85
What happens do groundwater levels after January and throughout the winter?
Groundwater levels then decline throughout the late winter, spring and summer, reaching their lowest point in early autumn.
86
What are cyrospheric processes?
Ablation is a loss of ice from snow, ice sheets and glaciers due to a combination of melting, evaporation and sublimation.
- Meltwater is an important component of river flow in high latitudes and mountain catchments in spring and summer.
- Rapid thawing of snowing upland Britain in winter is a common cause of flooding in adjacent lowlands (e.g. Welsh uplands and the Lower Severn Valley, Pennines and the Vale of York)
87
What are the main processes involved in the exchange of carbon?
The main processes involved in carbon exchanges (or fluxes) are: precipitation, photosynthesis, weathering, respiration, decomposition and combustion.
88
Describe how carbon is exchanged through precipitation
- Atmospheric carbon dioxide dissolves in rainwater to form weak carbonic acid. This is a natural process. However, rising concentrations of carbon dioxide in the atmosphere, due to anthropogenic emissions, have increased the acidity of rainfall.
- This has contributed to increased acidity of ocean surface waters with potentially harmful effects on marine life.
89
Describe how carbon is exchanged through photosynthesis
- The flux of carbon from the atmosphere to land plants and phytoplankton via photosynthesis averages around 120 giggatonnes (GT) a year.
- Using the sun's energy, carbon dioxide from the atmosphere and water, green plants and marine phytoplankton convert light energy to chemical energy (glucose) through the process of photosynthesis.
- Plants use energy in the form of glucose to maintain growth, reproduction and other life processes. In doing so they release carbon dioxide from the atmosphere in respiration.
90
Describe how carbon is exchanged through weathering
- Weathering is the in situ breakdown of rocks at or near the Earth's surface by chemical, physical and biological processes.
- Most weathering involves rainwater which contains dissolved carbon dioxide, derived from the soil as well as the atmosphere.
- Rainwater is a weak carbonic acid, which slowly dissolves limestone and chalk in a process known as carbonation.
- Carbonation releases carbon from limestones to streams, rivers, oceans and the atmosphere. The process is most effective beneath a soil cover because the higher concentration in the soil makes rainwater highly acidic.
91
How much carbon does chemical weathering transfer a year?
It is estimated that chemical weathering transfers 0.3 billion tonnes of carbon to the atmosphere and the oceans every year
92
Describe how carbon is exchanged through respiration
- Respiration is the process in which carbohydrates (e.g. glucose) fixed in photosynthesis are converted to carbon dioxide and water.
- Plants and animals absorb oxygen which 'burns' these carbohydrates and provides the energy needed for metabolism and growth.
- Respiration is the reverse of photosynthesis. Whereas photosynthesis absorbs carbon dioxide and emits oxygen, respiration absorbs oxygen and releases CO2.
- Respiration and photosynthesis are the two most important processes in the fast carbon cycle.
- The volume of carbon exchanged by respiration and photosynthesis each year is one thousand times greater than that moving through the slow carbon cycle.
93
Describe how carbon is exchanged through decomposition
- Decomposer organisms such as bacteria and fungi breakdown dead organic matter, extracting energy and releasing CO" to the atmosphere and mineral nutrients to the soil.
- Rates of decomposition depend on climatic conditions.
- The fastest rates occur in warm, humid environments such as the tropical rainforest.
- In contrast, decomposition is slow in cold environments like the tundra or drylands such as tropical deserts.
94
Describe how carbon is exchanged through combustion
- Combustion occurs when organic material reacts or burns in the presence of oxygen. The combustion process releases CO2 as well as other gases such as sulphur dioxide and nitrogen oxides.
- Combustion is a natural fuel use in many ecosystems. Wildfires caused by lightning strikes are essential to the health of some ecosystems such as the coniferous forests of the Rocky mountains.
- Long, cold winters slow the decomposition of forest litter which builds up on the forest floor. Fire shifts this log jam, freeing carbon and nutrients previously inaccessible to forest trees. It also opens up the forest canopy, creating new habitats and increasing biodiversity.
- Combustion also results from human activities such as the deliberate firing of forest and grassland in order to clear land for cultivation or improve the quality of grazing.
- More important is the combustion of fossil fuels. despite international efforts to curb CO2 emissions, oil, coal and natural gas power the global economy and their consumption continues to grow.
95
How much carbon is transferred per year through the burning of fossil fuels?
10 GT of CO2 a year from the geological store to the atmosphere, oceans and biosphere.
96
What is carbon sequestration in the oceans?
Carbon sequestration is the process in which the oceans 'take up' carbon by two mechanisms (physical pump and biological pump)
97
Describe the physical (inorganic) pump
- Involves the mixing of surface and deep ocean waters by vertical currents, creating a more even distribution of carbon (both geographically and vertically) in the oceans.
- Initially carbon dioxide enters the oceans from the atmosphere by diffusion. Surface ocean currents then transport the water and its dissolved carbon dioxide polewards where it cools, becomes more dense and sinks. This downwelling occurs in only a few places in the oceans.
- One example of where downwelling occurs is in the North Atlantic between Greenland and Iceland.
- Downwelling carries dissolved carbon to the ocean depths where individual carbon molecules may remain for centuries.
- Eventually deep ocean currents transport the carbon to areas of upwelling. In these areas, cold, carbon rich water rises to the surface and carbon dioxide diffuses back into the atmosphere.
98
Describe the biological (organic) pump
- Around 50 GT of carbon is drawn from the atmosphere by the biological pump every year.
- Marine organisms drive the biological pump
- Phytoplankton (floating near the ocean surface) combines sunlight, water and dissolved carbon dioxide to produce organic material. Whether consumed by animals in the marine food chain, or through natural death, carbon locked in the phytoplankton either accumulates in sediments on the ocean floor or it decomposes and is released into the ocean as carbon dioxide.
- Other marine organisms such as tiny Coccolithophores, molluscs and crustaceans extract carbonate and calcium ions from sea water to manufacture plates, shells and skeletons of calcium carbonate.
- Most of the carbon-rich material ends up in the ocean sediments and is lithified to form chalk and limestone.
99
Describe the role of vegetation in holding carbon
Land plants, especially trees in the rainforest and boreal forests, contain huge stores of carbon. Most of this carbon, extracted from atmospheric CO2 through photosynthesis, is locked away for decades.
100
Describe the Amazon Rainforest
- Size: 6 million kilometres squared.
- Population: 30 million people
- Countries: The majority (70%) of the rainforest is located in Brazil, but the forest also extends into Peru, Ecuador, Venezuela, Colombia, Bolivia and Guyana.
- Rivers: Amazon River,
- Shape: Elevation is mostly 200 m or 500 m high
- Dominated by tall, evergreen, hardwood trees.
101
Describe the main pattern of temperature and rainfall in Manaus.
Average temperature is around 26.5°C, maximum temperature is around 31°C, and the minimum temperature is around 23°C. Precipitation is highest during March at around 312 mm, and lowest in August at 60 mm. Precipitation begins to increase in September and then decreases in April.
102
Explain how the pattern of temperature and rainfall is typical of an equatorial location.
High average temperatures are a response to intense insulation throughout the year. However, significant cloud cover ensures that maximum temperatures do not reach the extremes of subtropical 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.
103
Describe the main flows and stores in the Amazon water cycle.
- The main flows are precipitation, evapotranspiration and run-off.
- On the other hand, the main stores are the ground water/soil, vegetation, Amazon Basin, rivers and the atmosphere.
- Average rainfall is more than 2000 mm and it is fairly evenly distributed throughout the year, but short drier seasons occur in some areas. Around 10% of precipitation is intercepted by forest trees.
- High temperatures of the rainforest allow the atmosphere to store large amounts of moisture (e.g. absolute humidity is high). Relative humidity is also high.
- Rapid run-off 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.
104
Explain how temperature and rainfall are likely to influence the carbon cycle in Amazonia (give figures)
- High temperatures, high rainfall and intense sunlight stimulate primary production of carbon.
- NPP averages about 2500 grams/metres squared/year.
- Amazonia alone accounts for 15-25% of all NPP in terrestrial ecosystems.
- High temperatures and humid conditions promote rapid decomposition of organic litter by bacteria, fungi and other soil organisms. This increases the volume of carbon in the atmosphere, as decomposition emits carbon dioxide.
105
Which physical factors affect the flow and store of water in the Amazon rainforest?
- Geology: Impermeable catchments (e.g. large parts of the Amazon basin area ancient shield area comprising impermeable crystalline rocks) have minimal water storage capacity resulting in rapid run-off. Permeable and porous rocks such as limestone and sandstone store rainwater and slow run-off.
- Relief (slopes): 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 run-off. Widespread inundation across extensive floodplains (e.g. the Pantanal) occurs annually, storing water for several months and slowing its movement into rivers.
- Temperature: High temperatures throughout the year generate high rate 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.
106
Using a named example describe the human factors that affected the stores and flows of water in the Amazon rainforest
In the Upper Madeira drainage 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 run-off) and in the atmosphere. At the same time, fewer trees mean less evapotranspiration and therefore less precipitation. Meanwhile, total run-off and run-off speeds have increased, raising flood risks throughout the basin.
107
Which physical factors affect the stores and flows of carbon in the Amazon basin?
Temperature, precipitation, sunlight, decomposition, geology, and humidity.
- Forest tress dominate the biomass of the Amazon
- 100 billion tonnes of carbon is locked up in the trees
- Trees absorb 2.4 billion tonnes of carbon a year
- Plant growth is stimulated by sunlight, precipitation, etc.
- Trees release 1.7 billion tonnes of carbon a year
108
Describe some more human factors affecting carbon and nutrient flows and stores in the Amazon rainforest
- Tropical rainforest is a store of calcium, potassium, and magnesium.
- Rainforest soils contain only a small reservoir of essential nutrients and the forest is only sustained by a rapid nutrient cycle.
- Deforestation destroys the main nutrient store (trees) and removes most nutrients from the ecosystem. Nutrients no longer taken up by the root system are washed out of soils by rainwater; and soils without tree cover are eroded by run-off.
- No canopy layer causes heavy rain to leech the remaining nutrients in the soil. This causes the soils nutrient fertility level to become even lower.
- Human actions expose the soil which degrades the soil and nutrients.
Why is the need for management of the Amazon rainforest to maintain the water
109
Describe the human factors affecting carbon and nutrient flows and stores in the Amazon rainforest
- Present-day deforestation is most present in tropical rainforest
- In primary rainforest, unaffected by human activity, the biomass of trees represents about 60% of all the carbon in the ecosystem. The above ground carbon biomass in the rainforest is 180 tonnes/ha. Most of the remaining carbon is found in the soil as roots and dead organic material.
- Deforestation decreases the carbon biomass store
- Croplands and pasture only contain a small amount of carbon compared to the trees.
- The biomass of grasslands in areas of former rainforest is 16.2 tonnes/ha; and for soya cultivation it is just 2.7 tonnes/ha
- Deforestation also reduces the inputs of organic material to the soil. Soil, depleted of carbon and exposed to strong sunlight, support fewer decomposer organisms, which reduces the flow of carbon from the soil to the atmosphere.
110
Why is the need for management of the Amazon rainforest to maintain the water and carbon cycle needed?
Without the trees, the water and carbon cycle cannot take place, because there is no evapotranspiration, little precipitation and there is no ground surface cover. This means that the water cycle cannot take place, and the conditions are unfavourable for decomposers and plants to grow for the carbon cycle. Therefore, management of the Amazon rainforest must take place, in order to ensure that the water and carbon cycle can still take place.
- The rainforest plays a national and international important role regarding climate change, so therefore it has to be managed so the implications of global climate change can be reduced.
- There are also many indigenous people which have been living there for over thousands of years, so rainforest has to be managed to maintain their habitats and livelihoods.
111
How does legislation help sustainable management of the rainforest?
- Brazil is committed to restoring 120,000 km squared of rainforest by 2030.
- Since 1998, the Brazilian government has established many forest conservation areas. These Amazon Regional Protected Areas now cover an area 20 times the size of Belgium.
- By 2015, 44% of the Brazilian Amazon comprised of national parks, wildlife reserves and indigenous reserves where farming is banned.
- The Parica project in Rondonia in the western Amazon aims to develop 1000 km squared commercial timber plantation on government-owned, tropical hardwood seedlings, planted on 4000 smallholdings, to mature over a period of 25 years. 20 million tropical hardwoods are being planted, these are expected to be cut down in 25 years, but this is being done in a manged way. Trees will be constantly, grown, cut down and replaced.
- 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 rainforest 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.
- The UN's Reducing Emissions from Deforestation and Degradation Scheme provides payment to the tribe for protecting the rainforest and abandoning logging.
- Agriculture is the main reason that the rainforest gets destroyed.
112
Describe the benefits of reforestation on the Amazon
- Water and carbon cycle will return
- Food source and livelihoods for the indigenous Surui people return.
- Habitats for animals return
- Nutrients in the soils return
- Biodiversity increases
- Climate can return to normal
- Water cycle and carbon cycle can return to normal.
113
Explain how improved agriculture techniques look to preserve the water and carbon cycle in the Amazon rainforest
- One response to improve agriculture has been diversification. Soil fertility can be maintained by rotational cropping and combining livestock and arable operations. Integrating crops and livestock could allow a fivefold increase in ranching productivity and help slow rates of deforestation.
- Human-engineered soils have also been proposed, which include creating 'dark soils' made from inputs of charcoal, waste and human manure. Charcoal in these soils attract microorganisms and fungi and allows the soils to retain their fertility long-term. If these soils can be successfully recreated they would allow intensive and permanent cultivation which would drastically reduce deforestation and carbon emissions.
- These two management strategies reduce deforestation, and so therefore mean that the water and carbon cycle can be preserved, because reintroducing/protecting trees means that the two cycles can take place.
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Describe the Arctic Tundra
- Arctic tundra occupies 8 million km2 in northern Canada, Alaska and Siberia.
- Extends from the northern edge of the boreal coniferous forest to the Arctic Ocean and its southern limit approximates the 10°C July isotherm.
- Climatic conditions in the tundra are severe and become more extreme with latitude.
- For 8 or 9 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 thawing during the summer.
- Permafrost underlies much of the tundra and is an important feature of the region's water cycle.
- In winter, when for several weeks the sun remains below the horizon, temperatures can plunge below -40°C. Long hours of sunlight in summer provide some compensation for brevity of the growing seasons.
- Mean annual precipitation is low.
- Few plants and animals have adapted to this extreme environment: biodiversity is low and apart from a few dwarf species, the ecosystem is treeless.
- In the southern areas - the Low Arctic - conditions are less severe, and vegetation provides continuous ground cover.
- Further north in the High Arctic, plant cover is discontinuous with extensive areas of bare ground.
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Describe the climate of Iqaluit-
- Iqaluit (Baffin Island, Canada)
- Highest temperature recorded: 16°C
- Lowest temperature recorded: -27°C
- Highest precipitation recorded: 61 mm
- Lowest precipitation recorded: 19.9 mm
- Highest precipitation and temperature values are recorded in July and August.
- Precipitation and temperature decrease after August and increase from February.
- Permafrost underlies much of the tundra
- Few plants and animals have adapted to this climate and environment, biodiversity is low.
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Describe the main features of water cycle in the Arctic Tundra
- Low annual precipitation (50-350 mm) with most precipitation falling as snow.
- Small stores of moisture in the atmosphere owing to low temperatures which reduce absolute humidity.
- Limited transpiration because of the sparseness of the vegetation cover and the short growing season
- Low rates of evaporation. Much of the sun's energy in 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. Impermeable permafrost.
- 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 summer. This temporary store of liquid water is due to permafrost which impedes drainage.
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Describe the main features of the carbon cycle in the Arctic tundra region
- Permafrost is a vast carbon sink
- Globally, it is estimated to contain 1600 GT of carbon.
- 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 five 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.
- Net primary productivity (NPP) is less than 200 grams/m2/year
- The tundra biomass is small, ranging between 4 and 29 tonnes/ha depending on the density of vegetation cover.
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Describe some more of the main features of the carbon cycle in the Arctic tundra region
- During the growing season plants input carbon-rich litter to the soil. The activity of microorganisms increases, releasing carbon dioxide to the atmosphere through respiration. However, carbon dioxide emissions are not just confined to the summer. Even in winter, pockets of unfrozen soil and water in the permafrost act as sources of carbon dioxide and CH4-.
- Snow cover may insulate microbial organisms and allow some decomposition to happen despite the low temperatures.
- In the past the permafrost has functioned as a carbon sink, but today: global warming has raised concerns that it is becoming a carbon source.
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Explain the physical factors (including seasonal changes) that influence the stores and flows of the water cycle
- Flow and stores of water in the tundra are influenced by temperature, relief and rock permeability.
- 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 (top metre) 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 occurs from standing water, saturated soils and vegetation.
- Humidity is low all year round and precipitation is sparse.
- 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 underlines 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.
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Explain the physical factors (including seasonal changes) that influence the stores and flows of the carbon cycle
- Carbon is mainly stored in decomposed plant remains which are frozen in the permafrost and remain there for hundreds of thousands of years often.
- Since temperatures are so low and water is mainly frozen, plants have limited access to nutrients, so carbon store of the biomass is small. However, there is compensation in the summer as there are long days of sunlight where photosynthesis takes place.
- Low temperatures and waterlogging slow decomposition and respiration and the flow of CO2 into the atmosphere
- Owing to the impermeability of the permafrost, rock permeability, porosity and the mineral composition of rocks exert little influence on the carbon cycle.
- Most of the carbo is locked away for 5000 years.
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Describe the human/ economic activities taking place in Alaska
- Oil and Gas was discovered in the Prudhoe Bay in 1968 - located in the North Slope of Alaska between the Brooks Range in the south and the Arctic Ocean in the north.
- Many challenges for the oil and gas industries: A harsh climate with extreme temperatures and long periods of darkness in winter, the melting of the active layer in summer, remoteness and poor accessibility, and a fragile wilderness of great ecological value.
- Production still went ahead driven by the high global energy prices and the US government policy to reduce dependency on oil imports.
- Large facilities, pipes, power lines, roads etc. were all put in place in the 1970s-1980s.
- 1990s- the North slope accounted for nearly a quarter of the USA's domestic oil production.
- Today = 6% though Alaska is still an important oil and gas province.
- Decline in recent years reflects two things: high production costs on the North Slope and the massive growth of the oil shale industry in the USA.
- 1985 - North Slope produced 1779 thousand/barrels/day out of 8971 thousand/barrels/day that the USA produced.
- 2014 - North Slope produced 479 thousand/barrels/day out of 8653 thousand/barrels/day that the USA produced.
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How is the exploitation of oil and gas impacted on the water and carbon cycle?
- Oil and gas exploitation on Alaska's North Slope has had significant impacts on the permafrost and on local water and carbon cycles.
- Permafrost is the major carbon store in the tundra, and it is highly sensitive to changes in the thermal balance. In many years, the balance has been disrupted by the activities of oil and gas companies which have caused localised melting of the permafrost.
- Melting of the permafrost 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, which increases absorption of sunlight, and removal of the vegetation cover which insulates the permafrost.
- Permafrost melting releases carbon dioxide and methane.
- On the North Slope estimated carbon dioxide losses from the permafrost vary from 7 to 40 million/tonnes/year.
- Gas flaring and oil spillages also input carbon dioxide to the atmosphere.
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How is the exploitation of oil and gas further impacted on the water and carbon cycle?
- Other changes to the local carbon cycle are linked to industrial development. For example, the photosynthesis and the uptake of carbon dioxide from the atmosphere; and the thawing of soil increases microbial activity, decomposition and emissions of carbon dioxide. Moreover, the slow-growing nature of tundra vegetation means that regeneration and recovery from damage takes decades.
- Similar changes have happened to the water cycle. Melting of the permafrost and snow cover increases run-off 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.
- In addition, drainage networks are disrupted by road construction and by seismic explosions used to prospect for oil and gas.
- Finally, water abstracted from creeks and rivers for industrial use and for the building of ice roads in winter reduce localised run-off.
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What management strategies are being introduced to moderate the impact on the water and carbon cycle in Alaska?
- Insulated ice and gravel pads
- Buildings and pipelines elevated on piles
- Drilling laterally beyond drilling platforms
- Powerful computers to detect oil and gas bearing geological structures remotely
- Refrigerated supports
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How do insulated gravel and ice pads moderate the impact on the water and carbon cycle in Alaska?
When infrastructure is built on insulated pads, it prevents the heat from above the ground going into the ground below. Prevents permafrost from melting
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How do buildings and pipelines elevated on piles moderate the impact on the water and carbon cycle in Alaska?
This allows cold air to circulate beneath heat-generating infrastructure that could melt the permafrost, thus insulating it. Stops heat from the buildings melting the permafrost layer.
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How does drilling laterally beyond drilling platforms monitor the impacts on the water and the carbon cycle in Alaska?
Since new drilling techniques allow for oil and gas to be accessed several kilometres from the drilling site, fewer drilling sites are needed so less vegetation is disrupted, and permafrost is protected. They now go horizontally underneath the ground to find the oil, only one drilling site is now used, this means that the impact above the ground is minimised.
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How do powerful computers to detect oil and gas bearing geological structures remotely monitor the impacts on the water and the carbon cycle in Alaska?
Fewer exploration wells are needed so the environment is less disrupted. Computers can now find sources of oil and gas more easily. Fewer infrastructure need, because there are fewer wells, so therefore there is less of an impact.
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How do refrigerated supports monitor the impacts on the water and carbon cycle?
Used on trans-Alaska pipeline to stabilise the temperature of the permafrost. Also used beneath buildings. Pipeline which takes oil to the USA is cooled, this is so that it doesn't warm up the land and cause thawing.
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What are ways in which the global carbon cycle is managed?
- Wetland restoration
- Afforestation
- Agricultural practices
- International agreements to reduce carbon emissions
- Cap and trade
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How is wetland restoration used to manage the global carbon cycle?
- The common features is that the water table is near the surface, include marshes, mangroves (areas which are waterlogged on a permanent basis)
- Contain 35% of the terrestrial carbon pool.
- The loss of wetland is due to urbanisation, population growth and economic development.
- To restore wetland, examples of methods are reconnecting an area of land to a river (water saturates the ground). To remove the drains and allow those areas to flood and be saturated again.
- Wetland areas have been drained to dry the land, so that it can be built on or farmed on.
- Sea defences can also be breached to saturate the land.
- In east Cambridgeshire, converted 400 ha of farmland back into wetland.
- Similar project happening in Somerset at the moment.
- 112,000 ha have been targeted for restoration in the Canadian prairies. They lost 70% of their wetlands in Canada. These new wetland will absorb 364,000 tonnes of carbon per year.
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How is afforestation used to manage the global carbon cycle?
- The planting of trees back into deforested areas and areas which didn't have trees before. Trees carbon sinks, so they reduce carbon in the atmosphere.
- Trees also reduce flooding, and soil erosion, and increasing biodiversity.
- Protecting the forests from deforestation is a cheap way of reducing greenhouse emissions.
- The UN have an organisation called REDD, which gives money to developing countries to conserve their rainforests and replant them. (The Red Scheme). Amazonia, Lower Mississippi.
- 1978, China afforested 14,000 km squared. Planted fast growing trees such as birch. They had soil issues (desertification), so the aim was to sort that out.
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How are agricultural practices used to manage the global carbon cycle?
- Unsustainable agriculture practices, such as overgrazing result in soil erosion and the release of large amounts of carbon dioxide released into the atmosphere.
- Overgrazing and under cultivating the land removes the nutrients, leading to drying-out of the land.
- Intensify livestock farming releases 100 million tonnes/year of methane.
- Ways to reduce the emissions include growing crops without ploughing soil, which preserves. Zero tillage.
- Polyculture: growing annual crops in disperse with trees, because trees provide protection from wind erosion.
- Controlling the amount of manure that livestock produce.
Contour ploughing: plough across the land, so gullies are not created and rainwater gets trapped. This stops the soil being eroded and therefore holds the carbon in the ground.
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How are international agreements to reduce carbon emissions used to manage the global carbon cycle?
International cooperation is needed to combat the impacts of climate change. Climate change affects all countries.
- Historically, countries haven't wanted to do cooperate, because by polluting they are boosting their economy.
- Kyoto protocol (1997) was an international agreement to combat climate change.
- Under Kyoto most rich countries agreed to legally reduce carbon dioxide emissions, though developing countries and some of the biggest polluters (e.g. China and India), were exempted. Also, several rich countries, such as USA and Australia refused to ratify the treaty.
- Kyoto expired in 2012. A new international agreement was reached at the Paris Climate Convention in 2015 for implementation in 2020.
- The Paris agreement aims to reduce global carbon dioxide emissions below 60 % of 2010 levels by 2050, and keep global warming below 2 degrees celsius.
- However, countries will set their own voluntary targets, which are not legally binding and a timetable for implementing them has yet to be agreed. Rich countries will transfer significant funds and technologies to help poorer countries achieve their targets.
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How is cap and trade used to manage the global carbon cycle?
- Known as a market based approach to limit carbon dioxide emissions.
- Under this scheme, businesses are allocated an annual quota for their carbon dioxide emissions.
- If businesses emit less than their quota, they receive carbon credits which can be traded on international markets.
- Businesses that exceed their quotas must purchase additional credits or incur financial penalties.
- Carbon offsets are credits awarded to countries and companies for schemes such as afforestation, renewable energy and wetland restoration.
They can be bought to compensate for excessive emissions elsewhere.
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What are ways used to manage the global water cycle?
- Forestry
- Water allocations
- Drainage basin planning
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How is forestry used to manage the global water cycle?
- The crucial role of forests in the global water cycle is recognised by multilateral agencies such as the United Nations and World Bank.
- The UN and WB together with other organisations and governments, fund programmes to protect tropical forests.
- The UN's Reducing Emissions from Deforestation and Forest Degradation (REDD) programme and the World Bank's Forest Carbon Partnership Facility (FCPF) fund over 50 partner countries in Africa, Asia-Pacific and South America.
- Financial incentives to protect and restore forests are a combination of carbon offsets and direct funding.
- Brazil has received support from the UN, World Bank, World Wildlife Fund (WWF) and the German Development Bank to protect its forests.
- The Amazon Regional Protected Areas (ARPA) programme now covers nearly 10% of the Amazon Basin. Areas included in the programme are strictly protected.
- The benefits are significant: stabilising the regional water cycle; offsetting 430 million tonnes of carbon a year; supporting indigenous forest communities; promoting ecotourism; and protecting the genetic bank provided by thousands of plant species in the forests.
- Has an impact on the systems that take place
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How are water allocations used to manage the global water cycle?
- In countries of water scarcity, governments have to make difficult decisions on the allocation of water resources.
- Agriculture is by far the biggest consumer. Globally it accounts for 70% of water withdrawals and 90% of consumption.
- Wastage of water occurs through evaporation and seepage through inefficient water management (e.g. over-irrigating crops).
- Improved management techniques which minimise water losses to evaporation include mulching, zero soil disturbance and drip irrigation.
- Losses to run-off on slopes can be reduced by terracing, contour ploughing and the insertion of vegetative strips.
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How are water allocations used to manage the global water cycle (further)?
- Meanwhile, better water harvesting, with storage in ponds and reservoirs, provides farmers with extra water resources.
- Recovery and recycling of waste water from agriculture, industry and urban populations is technically feasible, but as yet little used outside the developed world.
- In semi-arid regions of water scarcity, such as the Lower Indus Valley in Pakistan, and the US Colorado Basin, water agreements divide up resources between downstream states.
- In Pakistan the Punjab and Sindh receive 92% of the Indus's flow; in the Colorado Basin water resources are allocated to California, Arizona, Nevada, Utah and New Mexico.
In both regions, the vast bulk of water is used for irrigation.
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How is drainage basin planning used to manage the global water cycle?
- The management of water resources is most effective at the drainage basin scale. At this scale it is feasible to adopt an integrated or holistic management approach to accommodate the often conflicting demands of different water users.
- Agriculture, industry, domestic use, wildlife habitats, biodiversity and so on.
- Specific targets for drainage basin planning include run-off, surface water storage and groundwater. Rapid run-off is controlled by reforestation programmes in upland catchments, reducing artificial drainage and extending permeable surfaces (e.g. gardens, green roofs) in urban areas.
- Surface water storage is improved by conserving and restoring wetlands, including temporary storage on floodplains. Groundwater levels are maintained by limiting abstraction (e.g. for public supply, faming and industry) and by artificial recharge, where water is injected into aquifers through boreholes.
- In England and Wales drainage basin management is well advanced. Under the EU's Water Directive Framework, ten river basin districts have been defined.
- The districts comprise major catchments, such as the Severn, Thames and Humber. Each district has its own River Basin Management Plan published jointly by the Environment Agency and Defra (Department for Environment, Food and Rural Affairs). The plan sets targets in relation to, for example, water quality, abstraction rates, groundwater levels, flood control, floodplain development and the status of habitats and wildlife.
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How is drainage basin planning used to manage the global water cycle? (further)
- In England and Wales drainage basin management is well advanced. Under the EU's Water Directive Framework, ten river basin districts have been defined.
- The districts comprise major catchments, such as the Severn, Thames and Humber. Each district has its own River Basin Management Plan published jointly by the Environment Agency and Defra (Department for Environment, Food and Rural Affairs). The plan sets targets in relation to, for example, water quality, abstraction rates, groundwater levels, flood control, floodplain development and the status of habitats and wildlife.
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