Soils, vegetation, desertification, management

Question 1

Arid

Answer 1

Areas with a permanent rain water defect and less than 250mm rain per annum

Question 2

Semi arid

Answer 2

Commonly defined as having rainfall of less than 500mm per annum

Question 3

how do deserts receive runoff

Answer 3

from ephemeral or short lived streams fed by rain and snow from adjacent highlands

Question 4

what are halophytes and how do they adapt to saline arid soils?

Answer 4

halophytes = a plant that can withstand high levels of salinity arid soils = poor, alkaline soils mean salts are common in soil and water (especially costal deserts e.g. Atacama) they adapt by having a higher than average cell osmotic pressure to counter act the alkaline affect e.g. salt bush some avoid salt by growing in the rainy season when salt concentrations are less date pass can grow in saline groundwater

Question 5

list of adaptations plants have for avoiding and tolerating heat

Answer 5

Cacti can withstand up to 65 degrees Spine shades keep them cooler than the surrounding air, lowering the temperature of the surface of the cactus Leaves of desert plants tend to be small and narrow - enables leaf temperature to be near air temperature even when stomata are closed Steeper leaf angles - reduce solar interception at midday when the air temp is most severe Colour: blue/grey/green leaves to reduce heat absorption E.g. Low Bluebush, found in the Australia Desert by Roxby Downs

Question 6

name of plant adapted to tolerate a lack of rainfall

Answer 6

xerophyte

Question 7

evidence for climate change in hot and semi arid environments

Answer 7

climate change = decades measured through rainfall records/thousands of years ancient and degraded sand dunes in areas that are now rainy e.g. Savannah in Africa now has 1000m of rainfall a year wadis provide evidence of former rivers and drainage systems in areas that are now much drier e.g. Egyptian desert former shorelines and beach features in areas that are now much drier e.g. Lake Chad in the Sahra was once 300,000q km in area dating back to 7000BC anthropological evidence e.g. archeology human life required a water source e.g. Garamantes civilisation in the Ahaggar Mountains, Sahara left behind cave paintings as early at 6000 BC

Question 8

how does climate change naturally cause desertification

Answer 8

There is periodic/episodic natural climate variability. For example, the Sahel has long experienced a series of historic droughts, dating back to the 17th century. This has occurred periodically in the 1910s, and then the 1940s and then the 1960s-1980s.

Question 9

how does human induced climate change cause desertification

Answer 9

Global warming arguably increases evapotranspiration, reduces biodiversity and decreases rainfall in drylands. However, carbon dioxide is a major resource of plant productivity, so some dryland species may favourably respond to this increase; this may lead to changes in species composition and abundance. Thus, human induced climate change may increase diversification risk, but the consequences of a loss of diversity are complex and many geologists and scientists have contrasting opinions.

Question 10

example of an impoverished arid area

Answer 10

Niger, with a HDI of 0.253 and a GDP per capita of $1069; meaning they remain in stage 3 of the DTM with some of the highest population growth rates in the world.

Question 11

explain how the human activity of deforestation could cause desertification

Answer 11

This occurs as fuel wood is collected by the uprooting of woody species; particularly problematic outside large urban areas where the urban poor can’t afford electricity. The direct removal of vegetation results in a deterioration of the soil - vegetation has a major role in determining the biological composition of the soil, as it has a function in nutrient recycling. The rate of erosion and runoff decrease exponentially with increased vegetation cover; dry soil that is not protected blows away with the wind, or s washed away by flash floods, leaving infertile lower soil layers. This soil then becomes an unproductive hardpan through evaporation.

Question 12

explain why desertification inducing human activity is most common in LIC areas

Answer 12

These intense population pressures lead to the exploitation of marginal lands for farming. This occurs as areas of unfavourable agro-climatic conditions, an absence of infrastructure and access to markets, poorly adapted production techniques and malnourished and undereducated population, become marginalised. A lack of development and investment by government means that there is increased population pressure on the carrying capacity of the area, giving rise to overgrazing, over-cultivation and deforestation.

Question 13

describe/explain colour of soils in arid areas vs semi arid areas

Answer 13

SEMI: Increased organic matter (more rainfall provides fertile ground for plant growth) may be enough to colour the top soil to create chestnut-brown soils. Increased rainfall also means increased hydrolysis, which creates reddish brown soils ARID: tend to be grey in colour due to a lack of moisture BOTH: high salt content forming Solonetz of Solonchak soils in the upper horizon Solonetz: sodium chloride; black Solonchak: sodium carbonate; white

Question 14

solonetz soils

Answer 14

sodium chloride black

Question 15

solonchak soils

Answer 15

sodium carbonate white

Question 16

describe/explain how duricrusts are a characteristic of arid and semi arid soils

Answer 16

Duricrust is a hard horizon at the surface or just below the surface, between a few cm and a m in size; deeper in wetter areas, and in dry areas it remains at the surface. They form as material is leeched, duricrust remains and evaporations then leaves salt behind. This is most evident in salt plans, which are essentially salt duricrusts that have accumulated and salinized at the surface. This makes the surface of the soil hard.

Question 17

describe/explain how high levels of salinity are a characteristic of arid and semi arid soils

Answer 17

IRRIGATION: As water is put on corps and evaporates, salt is left behind; this is famously seen in Pakistan, which have participated in widespread irrigation since 800 BC. CAPILLARY ACTION: salt deposits can be evident as the little soil moisture that exists is drawn upwards by capillary action and may leaving deposits at the surface.

Question 18

describe/explain how organic content and depth of soil are a characteristic of arid and semi arid soils

Answer 18

low organic content (less than 1%) due to a lack of vegetation (because of a lack of rainfall) Soils are less superficial, occurring at a deeper level than in hot arid environments as there is more rain. They are therefore not subject to the same level of erosion and transportation that hot arid soils are, as semi-arid soils are not as loose and thin.

Question 19

case study example of Africa’s farmer managed land regeneration as a method for reducing desertification impact

Answer 19

‘Great Green Wall’ stretching from Senegal to Djibouti on the horn of Africa, cutting across the Sahel and the Sahara. Countrywide, 11.4m trees have been planted since 2007 and the scheme has provided gardeners seeds, local staff employment, paid for water bills, bringing in water systems, fertilisers and barbed wire for security. By enabling better farming practices through providing resources, employment and training, the GGW has enabled native sprouting tree growth, increasing soil water retention and decreasing evaporation. E.g. 500 Malian men are trained in a migrant camp in Niger. In this scheme, plants have been used to enrich the soil and restore its fertility. For example, leguminous plants which extract nitrogen from the air and fix it into the soil. The overall restorative effect of this: in Ethiopia, 15m hectares of land have already been restored; in Nigeria, it’s 5m, and in Sudan, 2,000m.

Question 20

physical adaptations for animals to avoid/tolerate extreme desert temperatures

Answer 20

For example, beetles and scorpions can withstand temperatures of up to 50 degrees. Anatomical: light coloured bodies (reducing heat intake), thin body forms e.g. gazels. desert fox have large ears (with a large number of blood vessels), wet noses in order to increase the heat evaporation rate from their body, cooling them down. ostriches have bare head, throat legs to allow for cooling. long legs keep the body separated from the extreme ground temperatures

Question 21

behavioural adaptations for animals to avoid/tolerate extreme desert temperatures

Answer 21

BEHAVIOURAL 75% of animals in hot arid environments are nocturnal to avoid high day time temperatures. For example, the white-throated wood rat, create burrows lining them with scavenged debris. This allow them to escape from desert temperatures externally, but it keeps their habitat insulated (for night) by not allowing cool air to escape. The round-tailed ground squirrel, resort to estivation. During the summer months (that can be up to 50 degrees in Death Valley, California), they slow down their metabolism to conserve water and energy. Sand snakes move by side winding meaning only a small part of their body is in contact with sand; lizards assume an erect position when running, keeping their bodies off ground

Question 22

how can plants adapt behaviourally to a lack of rainfall (physical drought) in arid environments

Answer 22

BEHAVIOURAL: germination The seeds remain dormant and survive in the dry environment; when conditions are favourable the seeds germinate and the plants exploit the wet conditions. For example, Hogweed (found in Sahara), takes 8-10 days for the seed production process – seeds are produced quickly before the water runs out, when insect pollinators are abundant. In the same way, cytobiotic plants respond to a lack of rainfall by reproducing when the environment becomes hospitable: suppressing the flowering and sprouting. For example ironwood and smoke wood have seeds which will only germinate after severe mechanical abrasion during floods.

Question 23

name of plants adapted to physical drought

Answer 23

Xerophyte

Question 24

how can plants adapt physically to a lack of rainfall in arid environments?

Answer 24

Anatomical Small leaves of vegetation reduce the rates of water loss and evapotranspiration in plants. (physiological)Plants can diurnally close stomata, giving them a means of conserving water High water storage capacity, with heavily waxed in their stems to reduce circular water loss. Examples include the cotton-top cactus, and the prickly pear that have a swollen or fleshy appearance due to the high amount of water storage in them. Plants can be succulent by having shallow and wide roots that trap rainfall or dew that may collect at the surface, or long and deep in order to reach a more permeant water supply, as with phreatophytes e.g. mesquites.

Question 25

how can animals adapt behaviourally to a lack of rainfall in arid environments?

Answer 25

75% of animals in hot arid environments are nocturnal or subterranean to avoid high day time temperatures, preventing excess water loss. E.G. desert toads burrow themselves under desert debris, only emerging when a water source is detected. These areas can also be permanently or temporarily moister e.g. subterranean rock fissures. Gazelles don’t drink water or urinate if there is a lack of rainfall; getting water from their diet instead (like herbivores e.g. eland) Their urine is converted to uric acid as a white pellet instead of hydraulically expensive liquid waste

Question 26

example of an animal with a unique adaptation to the high saline content in water of arid environments

Answer 26

Road Runner Bird if there is high salt, the bird secrets excess salt from a gland near its eye

Question 27

example of an coastal animal that can uniquely obtain water in the low rainfall arid environments

Answer 27

Fogstand Beetle, Namib Desert Africa Fresh water is limited Close proximity to sea Receives fog in the cool hours of the morning Licking fog drenched rocks Fogstand beetles stand still, letting the off condense on their bodies, forming water droplets which they drink

Question 28

contrast biodiversity in the sonoran desert and the atacama desert

Answer 28

Sonoran: reasonable Atacama: limited

Question 29

what are phreatophytes

Answer 29

deep rooted plants that can reach down to the water table e.g. date palm

Question 30

contrast biomass in tropical areas and desert areas

Answer 30

tropical - 250,000kg per hectare desert - 500 kg per hectare

Question 31

how is sustainable development applied to arid areas

Answer 31

using land so it provides income for th local people but does not become degraded or desertified achieved through careful and strategic management strategies e.g. mining in such a way it extracts benefits from the environment but does not result in long term damage

Question 32

what are the climactic challenges of sustainable development in Egypt

Answer 32

high temperatures central and southern, in summer high average can exceed 40 degrees March-May khamasin (flow of dry air) can push temperatures up to 45 and humidity lower than 5% low and unreliable rainfall south of Cairo, average of nearly 0mm in central and southern

Question 33

what are the socio-economic challenges of sustainable development in Egypt

Answer 33

fertility rate 3,3 births per 1000 rural areas = family as economic strength/islamic gov resistance to birth control water for farming comes from the Nile but countries such as Ethiopia threaten to reduce this availability: building the Grand Ethiopian Renaissance Dam also pesticides and fertilisers washed in from downstream lack of regulation of industry and farming political instability strong military presence and threat of coups - deters investment and tourism/ high inflation and unemployment gov and citizens put short term goals ahead of long term sustainability

Question 34

what are the political problems with sustainable development in LIC countries

Answer 34

decades of bureaucracy and local government corruption (bribery, embezzlement) deeply ingrained culture long time to change attitudes combatting soil degradation and desertification would need to be part of reform to other aspects of development e.g. corruption, poverty and political instability

Question 35

what are the economic problems with sustainable development in LIC countries

Answer 35

lack of capital for infrastructure development, e.g. foreign aid organisations due to political instability social unrest threats from terrorism thus initiatives are limited and piecemeal easier to achieve in other HIC countries e.g. Australia/USA

Question 36

explain and evaluate how encouraging crop diversity can help to sustainably solve soil degradation

Answer 36

Encouraging crop diversity as water varies in quantity and quality across Egypt.

Government has encouraged the growth of sugarcane by establishing factories; in the northern delta where the land is affected by a high water table and increased salinity, rice crop has been encouraged (as it can resist relatively saline water)

However, the ability to train and educate agricultural workers would be far easier in HIC countries such as Australia and the US.

Question 37

explain/evaluate how better irrigation can help to sustainably solve soil degradation

Answer 37

Better irrigation strategies, leaving behind traditional field ditches in favour of buried low pipe Mesas.

This prevents evapotranspiration and unnecessary leakage, preserving the water for irrigation. IN the context of possible decreasing water supply due to Ethiopia’s Renaissance Dam.

BUT there is poor local management, embezzlement and bribery; a culture that is deeply engrained in Egypt and will take at least a generation to change

Question 38

explain how aquaponics can help to sustainably solve soil degradation

Answer 38

Aquaponics involves growing plants such as cucumber and tomato’s in hydroponic trays and farming fish (that can resist a slight ph. change), watering olive trees all using the same fresh water system.

Chemical inputs are avoided by using organic pest control e.g. ladybirds that kill aphids.

Reduces water loss greatly

Question 39

example of excessive deforestation causing soil degradation

Answer 39

in the sahel, national fuelwood consumption was estimated to be 8 times higher than the natural growth of forests

Question 40

explain how deforestation leads to soil degradation

Answer 40

reduced vegetation cover (little vegetation to begin with)

exposed soils to increased wind and occasional water erosion

no inputs of nutrients and organic matter via decomposition of leaf litter

Question 41

example of how excessive deforestation can be managed

Answer 41

improving the efficency of household stoves so they burn less fuel

subsitute fuels e.g. kerosene (more expensive)

Question 42

explain how unreliable rainfall is a problem for sustainable development

Answer 42

sustainable developement requires productive agriculture, so cant occur when rain restricts plant growth

Question 43

explain why high temperatures are problematic for sustainable development

Answer 43

increases soil salinity

via increased capillary action and evapotranspiration

reduces plant growth

Question 44

explain how desertification and soil degradation are probematic for sustainable development

Answer 44

limited carrynig capacity

attempts to increase productivity fail

inability to accomdate high birth rate

Question 45

explain how human geography can be problematic for the sustainable managment of arid areas?

Answer 45

high population growth, conservative societies, corruption, poverty

factors are embedded and difficult to change without large scale intervention often internationally

e.g. if sustainable development is met with corruption then they will stagnate

Question 46

outline the process of soil degradation

Answer 46

the loss of organic matter in the humus layer of soil

this degrades soil as the sticky nature of the humus binds the soiil together - removing it fragments the soil reducing the quality

the loss of strucutre and horizons in the soil

mature soil has 2/3 horizons clearly defined by colour and composition, poor soil has fewer and less defined structure

raised ph via toxic mining waste causing acidification

the emergence of duricusts aids this as hard crusts on top of the soil prevent plant oots from developing and anchoring the soil (erosion)

toxic mining waste can prevent plant growth and lower the soils ph vi

Question 48

what are the human factors that influence soil degradation

Answer 48

overgrazing

acidifiction

poor agricultural managment

construction of roads and tracks

deforestation

Question 49

explain the impliations of overgrazing on soil degradation

Answer 49

greater demand for food, employment

overgrazing: excess animals graze, consuming the organic matter, there is a loss of the binding effect plants have via their sticky nature and their contribution to the nutrient cycle

on marginal land

deforestation

Question 50

explain how deforestation influences soil degradation

Answer 50

people require firewood (not in arizona or HIC countries)

reduced vegetation cover (little vegetation to begin with)

exposed soils to increased wind and occasional water erosion

no inputs of nutrients and organic matter via decomposition of leaf litter

e.g. on the outskirts of the Sahel there is no gas avalible, kerosine is too expensive

Question 51

explain how poor agricultural managment influence soil degradation

Answer 51

short term needs of farmer (income and food) put above the long term degradation of the soil

planting too mcuh soil on slopes and ploughing horizontally not veritcallly (poor education) leading to the formation of rills and gullies, leaving the soil vlunerable to water erosion

HIC countries are regulated, marginal land is not used

Question 52

explain how the construction of roads and tracks influences soil degradation

Answer 52

compacting the soil

lowering the ability for plant growth and infiltration

more localised

Question 53

explain how climate change (physical and human) influences soil degradation

Answer 53

human induced occurs more quickly, decades

natural occurs minimally over a century

this involves a temp. increase leading to more evapotranspiration occuring form the minimal rainfall and capillary action that occurs

or it involves increase in unrelibale or intense rainfall - flash floods, leading to water erosion worsened

BUT can be benefical: more carbon dioxide alows for more plant growth, increase in average temperatures accelerates organic decay

Question 54

explain how soil degradation is influenced by wind and water erosion

Answer 54

water erosion is more prevelant in semi arid areas

wind erosion more prevelant in arid areas

soil is dry and dusty so is fragile, exacerbating:

water: 60% of soil degradation. surface runoff from flash floods creates rills and gullies in the soil that are prone to sheet wash or sheet flow
wind: removees dust and fine material from the surface, superfically

Question 55

example of agricultural mismanagment causing soil degradation

Answer 55

in eastern china

cultivation of sleep slopes

e.g. on slopes of less than 5 degrees there is a 100x smaller loss of soil than slopes of 25 degrees

if terraced the loss is smaller

Question 56

example of overgrazing leading to soil degradation

Answer 56

Mongolia over 130,000 hectres of land degradesd i this way

animals exceed carrying capacity

Question 57

impacts of desertification socio-economically

Answer 57

social

forced migration due to food scarcity and so social tension in migrant reception areas

economic

reduced income from pastoralism and food crops

decreased fuel and wood avalibility (kerosine more expensive alterntive)

dependency on food aid

Question 58

problems with combatting desertification in china

Answer 58

legislation is incomplete

enforcement is unreliable

rate of desertifiation managment less than development rate

shortage of funds

Question 59

how can overgrazing as a cause of soil degradation/desertification be managed

Answer 59

improved stock quality

vaccination programmes, introducing better breeds, yields of milk wool and meat increasde without increased herd size

reducing herd sizes

grazing over wider areas

Question 60

how is desert soil problematic for sustainble development

Answer 60

low precipitation = limited biomass to provide humus and nutrients,

in semi arid areas accumulation of organic matter is sufficient to colour the top 25 cm and help in moisture retention

generally alkaline, shallow and lacking clear horizons

high evaporation rates will bring salts to the near surface and may pose problems with some forms of irrigation

because of fragility of the soils they are prone to erosion with removal of vegetation and from over grazing and over cropping which may lead to desertification

Question 61

what are the overall impacts of unsustainable managment in the Aral Sea

Answer 61

dust storms (ten a year, affected up to 500km away)

human health (pollution, lack of fresh water: cancer, lung disease, high child mortality)

fishing (from 43,000 to 0, ship graveyards)

climate impact (winters are longer and colder, summer shorter and hotter, rainfall decreased less evapo.)

desertification (saliinzation at surface, excessive fertiliser: declline in vegetation 40% and increase winds - less vegetation)

Question 62

why was the aral sea unsustainably managed

Answer 62

the USSR ignored the environmental impacts of water diversion, environmental protection given a low priority and there was no opposition movement to change this

Question 63

how was the aral sea unsustainably managed

Answer 63

water diverted from two major rivers

part of five year plans funding irrigation for cotton

less water entered the sea - 23m lower sea level

decrease in sea level over time: as the sea became shallower there is less water for the sun to heat so higher temperatures more evapouration

soil salinity increased by 800%

Question 64

benefits of sustinable managment

Answer 64

stem out migration

provide indirect employment via multiplier effcet

jobs as drivers guides park rangers

alleviate poverty

Question 65

why is tourism in Namibia sustainable

Answer 65

It considers and balances the opportunities and costs of the environment. It incorporates long term strategic planning that allows for opportunities e.g. tourism to be balanced against challenges.

Planning in the background of enlightened ecological awareness: conservationism and sustainability.

Question 66

example of sustainable use of an arid environment (in physical and human terms)

Answer 66

_Damaraland camp (1996) is compatible with the physical environmen_t

It restricts guests to twenty, with ten en-suite rooms in total

It is built in cohesion with the environment, with tents raised on platforms

No swimming pool due to high water consumption; gorge plunge pool instead

Damaraland camp (1996) is compatible with the human environment

The majority of the 18 staff from the local area

Manager was previously a goat herder – knowledge and understanding of the demands of the area

10% of the profit from Wilderness safaris is reinvested (mobile clinics, education, running water, anti-poaching patrols)

Question 67

case study impacts of unsustinable managment of arid area

Answer 67

Water level of the lake reduced by 23m; once the 14th biggest lake in the world was 10% of its original size

Salinization at the surface lead to the 40% decline in vegetation and subsequent increase in winds (due to reduction in protection, friction inducing vegetation)

Lack of fresh water as the lake polluted by excessive fertiliser caused health problems (cancer, lung diseases, high child mortality rates 75 in 1,000)

Fishing decreased from one-sixth of the Soviet union’s entire fish catch to 0

However, in North Aral small dam implemented in 2005, which lead to a sea level rise of 8m and increased fish stocks

Question 68

why has using aquaponics to sustainably manage Egypt’s aridity been criticised

Answer 68

Large capital investment is unlikely given overseas aid is limited as organisations and countries are reluctant to expand their presence in Egypt due to terrorism, social unrest and political instability.

Difficult to do on a large scale, so appears to be a sticking plaster remedy

Question 69

why is sustainable managment possible in Namibia

Answer 69

This is possible because of the small population of 2.6 million and accompanying low population density

Currency created by gold silver and uranium stores

Background of a democratic, stable multiparty government; English speaking encouraging western visitation, international standing and investment

Question 70

list the problems to be overcome in the sustainable development of arid areas (case studies)

Answer 70

Low/unreliable rain (as little as 0mm in centeral and southern Africa, south of Cairo; north coast around 200mm from rain bearing winds from the sea)

High temperatures (central and south temperatures exceed 40 degrees, exacerbated by the Khamsin wind which causes humidity to drop to 5%; daytime temperatures moderated along North Coast by sea)

Poor soil quality (saline, duricrusts, low organic content, fragile)

Desertification/soil degradation (over-grazing, over-cultivation, acidification)

High population growth (Egypt: 3.3 births per thousand, families seen as a source of economic strength, Islamic gov. resists birth control)

Political instability (Egypt: president came to power in a coup 2013, deterring investment and tourism); economic difficulty (high levels of inflation and unemployment, encouraging short term solutions)

Renaissance Dam in Ethopia may restrict water supply in the future (pesticides and fertilisers are washed into the Nile).

Land use, ineffective or ignorant management of land (Aral Sea disaster: re-route two rivers to promote cotton plantation in the USSR. Lake shrank to 10% of its original size)

Question 71

explain and evaluate why desertification occurs due to climate change

Answer 71

periodic/episodic changes in climate

Naturally: The Sahel has long experienced a series of historic droughts, dating back to the 17th century. For example, during the 1910s, 1940s, 1960s-80s. BUT since 1980 rainfall has been increasing, due to enhancements in the African jet stream.

Human induced: global warming arguably increases evapotranspiration, reducing biodiversity and decreasing rainfall in drylands. Complex and not fully understood

Climate change can be positive: carbon dioxide is a major source of plant productivity; some dryland species may favourably respond to this increase changing the abundance and composition of species.

Question 72

where does human induced desertification happen the most

Answer 72

This occurs in poor areas such as Niger with a HDI of 0.253, remaining in stage 3 of the DTM with some of the highest population growth rates in the world.

Population pressure on carrying capacity of the area (absence of infrastructure, poor access to markets, unfavourable climate conditions).

Question 73

explain how over-grazing causes desertification

Answer 73

Overgrazing is the massive increase in sheep and cattle in semi-arid areas, the carrying capacity is exceeded; exacerbated by the installation of modern boreholes.

With a higher population, there is an increased need for subsidence and cash crop farming: as excess animals graze, removing the organic matter, there is a loss of the b binding affect plants have within the horizons of the soil and their contribution to the (fragile) nutrient cycle.

For example, in the Inner Mongolian Reigon of China, the density of animals exceeds the carrying capacity of 13,000ha of land.

Question 74

explain how salinisation (irrigation) can lead to desertification

Answer 74

Salinization due to badly managed irrigation.

If irrigated fields are poorly drained they become waterlogged and the surplus water evaporates, leaving poisonous salts.

If irrigation canals are badly lined water will leak out causing the water table to rise – if this occurs by more than 2/3m towards the surface, water is drawn up by capillary rise, evaporating, leaving salts.

If a high concentration of salt is deposited hard crusts called duricrusts are formed, sealing off water infiltration and plant or vegetation penetration: loss of vegetation and wildlife

Question 75

explain how deforestation can cause desertification

Answer 75

Deforestation is the direct removal of vegetation, resulting in the deterioration of the soil. This has reduced the vegetation cover, exposing the soil to increased erosion by wind and rainfall.

Additionally, the soil has been deprived of inputs of organic matter and decomposing leaf litter, depleting the quality of soil.

For example, in the Sahel, national fuelwood consumption was estimated to be nine times higher than natural growth. In the Sahel the only alternative is the expensive Kerosine gas, which outprices much of the community.

Question 76

how can wind and water erosion contribute to desertification

Answer 76

Water erosion is most prevalent in upper horizons of semi-arid areas, as these areas experience more frequent flash flooding. Surface runoff creates rills and gullies in the soil, that are prone to sheet wash and sheet flow.

For example in China water erosion contributes 46% of all desertification processes, particularly sandy desertification.

Wind erosion is most prevalent 3ft above the ground in the high energy hot arid environments – the lack of vegetation reduces the friction with the wind. Dust storms dislodge the upper horizons of the soil, degrading the soil.

For example, in China wind erosion contributes to 44% of desertification processes; 2/5 of soil lost in this way pours into the sea.

Additionally, wind can increase the temperature of an area e.g. Khamsin in Egypt, reducing the organic content of the soil further.

Question 77

describe how acification causes soil degradation

Answer 77

the increased subsistence and cash crop farming leads to the use of ammonia based fertiliser, that is applied to crops and lowers the pH of the soil. This restricts plant growth, leaving the soil barren – something that would be less likely in Arizona, California with better farming technology.

Question 78

list the methods of stopping/reversing desertification

Answer 78

fixing the soil

managed grazing

afforestation

farmer managed natural regeneration

development policy

Question 79

how can fixing the soil reverse desertification

Answer 79

Fixing the soil: shelter beds and windbreaks

Windbreaks are made from trees and bushes used to reduce soil erosion and evapotranspiration.

In Namibia sand fences have been constructed to stop the advance of dunes.

Also, in Xianjiang a windbreak forest system has been centred around an oasis, reducing wind velocity by 25%. This prevents the advancement of dunes, which is occuring at a rate of 3.5km a year, towards Beijing

Wind erosion contributes 44% of all desertification proceses.

Question 80

how can managed grazing reverse desertification

Answer 80

Fences with small paddocks, herds are moved between them with one or two days in between. This mimics natural grazing and allows the grass to grow optimally.

However in impoverished rural areas, inefficient agricultural management favoured as short term economic need is put before long term ecological need.

Question 81

how can reforestation reverse desertification

Answer 81

On a macro-scale, China has implemented a forest shelter bed development program in northern areas, protecting 11 million ha. of farmland.

In order to protect Beijing a nationwide campaign was initiated in 1991 involving the banning of the foraging and distribution of liquorice and two other wild plants.

These plants are illegally collected for the sale of herbal medicines, removing over one third of vegetation in western central china.

On a micro-scale, the Chinese government has employed locals to grow seedlings, which can be transported through established mechanisms to severely deforested areas during rainy seasons.

Educating the rural population about the dangers of deforestation and more efficient agricultural management has had large success. Forest cover has increased from 5% to 9%.

Long growth time before benefits are realized; development is occurring at a faster rate

Question 82

how can wider development policies combat desertification

Answer 82

these factors are embedded culturally, and take at least a generation to shift – as countries vulnerable to desertification move through the DTM attitudinal changes will accompany reduced population pressure.

For example, Egypt’s conservative government’s reluctant to promote universal, free contraception.

Tackling corruption in government: free up social services funding e.g. Mobutu’s DR Congo saw $5 billion stolen from the Congolese – money that could have, at least in part, promoted development via infrastructure projects, management strategies etc.

Question 83

describe the adaptations animals have for physical drought

Answer 83

Sexual maturity, mating and birth synchronised with favourable conditions.

Fast drinking of lasrge quantities of water, uptake of water from wet soil e.g. snails

Living temporarily in moister environments e.g. shrubs, stone in rock fissures below ground (75% of desert animals are subterranean, nocturnal or active when the surface is wet).

For example, desert toads burrow themselves under desert debris, only emerging when they detect water sources.

Gazelles don’t urinate during drought – when water is unavailable the gazelle can concentrate its urine into uric acid as a “white pellet” instead of expensive liquid waste.

Question 84

describe the adaptations of plants to combat physical drought

Answer 84

xerophytes e.g.. the creosote bush can survive up to a year without rain.

Dormancy of germination periods – water clocks of seed dispersal, in extreme years suppression of flowering and sprouting.

For example, the cytobiotic plants, ironwood and smoke wood, have seeds with coats so resistant that they will only germinate after severe mechanical abrasion following flash flooding. This germination process can be as swift as 8-10 days, in order that seeds are produced before the water runs out.

Fast growth of water roots after rain.

Effective water storage is useful in times of drought, such as heavily waxed stems, diurnally closing stomata and a swollen/fleshy appearance, seen in the cotton-top cactus.

Question 85

describe the adaptations of animals to physiological drought

Answer 85

Road runner bird secretes excess salt from a gland near its eye as a result of highly saline water. Fogstand beetle, found in the Namib desert (a close proximity to the sea) – when fresh water is very limited the fog that reaches the desert is condensed on the body of the beetle as they stand still, leading to water droplets forming which provides a freshwater source.

Question 86

describe the adaptations of plants to physiological drought

Answer 86

halaphytes

: Salt bush uptakes saline water and has a high salt tolerance due to a higher than average cell osmotic pressure to counteract the salinity. salt excreting glands

Question 87

describe the adaptations of animals to tolerate extreme temperatures

Answer 87

Some anthropoids such as beetles and scorpions can withstand temperatures of up to 50 degrees.

Light colours maximise reflection of solar radiation.

Desert foxes have large ears (with a large number of blood vessels) and wet noses to increase heat evaporation and cool them down.

Nocturnal, 75% of desert animals do this e.g. white-throated wood rat creates burrows using desert debris and scavenges to line it. This is insulated to not allow for cool air to escape, but also protects them from the extreme low night-time temperatures.

During the summer months, the round-tailed ground squirrel resorts to slowing their metabolism in order to conserve water and energy.

Question 88

describe the adaptations of plants to extreme heat

Answer 88

Cacti can survive up to 65 degrees.

They have physical adaptations such as small and narrow leaves, reducing evapotranspiration and enabling them to be near ambient temperature even when the stomata are closed.

Steeper leaf angles can reduce solar interception at midday, when the air temperature is most severe.

Plants have a blue grey green colour to reduce heat absorption e.g. low bluebush.

Question 89

describe the composition of duricrusts

Answer 89

High concentration of salt causes the breakdown of soil structure, causing crusts to form on the surface or subsurface –duricrusts.

They are either formed as calcrete of calcium carbonate (up to 40m comprising boulders, silt and gravel) or it can be silcrete, a crust cemented by silica.

Calcrete tends to be found in semi-arid areas, with between 200-500mm of rainfall.

On the other hand, silcrete is found in areas that have more than 50mm (not hyper arid), but have less than 200mm so are hot arid, and so are found in southern Africa and asutralia.

Question 90

describe biomass productivity

Answer 90

Biomass productivity is the rate of generation of biomass in an ecosystem. In arid areas, on average a net primary productivity of 90g/mg2/year – lack of organic matter; correlated positively with water activity).

Can be as low as 0 in hyper arid areas.

Extremes of heat and a lack of moisture mean there is very limited amounts of biomass and litter in arid environments.

Question 91

where are solonetz soils mainly found

Answer 91

semi arid reigons

with a higher proportion of clay and sodium

Question 92

how is vegetation different in semi arid and arid areas

Answer 92

Due to the higher amounts of rainfall, semi-arid vegetation can be more diverse with grasses, sage brush, some shrub layers and, in favoured locations, some trees.

Question 93

how is vegetation similar in semi arid and arid areas

Answer 93

vegetation has to adapt to the lack of moisture. As a consequence, xerophytic, phreatophytic and halophytic elements will appear in both.

water retention,

leaf adaptions,

stomata characteristics

depth of root systems

Question 94

what is the problem with a high salt content in soils

Answer 94

salts are poisonous to many plants

salts prevent plants from absorbing water into their roots

a high concentration of sodium salts causes DEFLOCCULATION (dispersal) of the soil particles; making the soil become impermeable and so plants can’t penetrate

loss of stickiness

Question 95

what are the causes of overgrazing

Answer 95

increase in herd size due to population growth

decrease in avalible grazing land because of increased crop cultivation