Ecosystems: Hot Semi-Arid Grasslands (WJEC Eduqas GCSE Geography B): Revision Note

Specification Link

This page covers part of 3.2.2 and 3.2.3 of the WJEC Eduqas GCSE B specification

3.2.2 - How are ecosystems damaged by human activity?

• How hot semi-arid grasslands have been damaged by human activity.

• How processes within the ecosystem have been affected

• The effects of the damage at the local scale, to include the effect on biodiversity, and at the global scale

3.2.3 - Why and how are ecosystems managed in a sustainable way?

• The reasons for conservation and management.

• The ways in which hot semi-arid grasslands have been managed

• Strategies for sustainable management.

Case Study: Human activity in the hot semi-arid grasslands

How human activity has damaged hot semi-arid grasslands

• Hot semi-arid grasslands provide water, grazing, food and fuel for millions of people

• The unique biodiversity of this biome encourages and supports wildlife tourism

• Human impacts are widespread

  • The main threats are:

    • Land use change

    • Landscape fragmentation, which disrupts herbivore communities

    • Climate change and rising atmospheric CO2

    • Unsustainable water use and irrigation methods

• Land clearance reduces grazing for animals such as giraffes and zebras

  • The clearance fragments the landscape, reducing movement between communities

• Large fires destroy plants - especially those which are not fire-resistant

  • Fires can also kill insects and small animals, providing food for predators

• Woody plants are killed by cattle eating their foliage, allowing thorny, animal-repellent trees to become dominant

• Poor agricultural practice can lead to soil degradation and desertification

• Overgrazing further exposes the grasslands to erosion

• Tourism involves the use of transport, which:

  • Damages vegetation

  • Disturbs wildlife

  • Affects breeding grounds

• Tourism also increases the amount of rubbish, which can harm animals

• Conservation in national parks is variable

  • Some parks attract illegal trophy hunting 

  • The value of products such as ivory and rhino horn, where the animal is killed just for their tusks, also increases poaching

    • Hunters target large males, leading to an imbalance in the population

  • Animals can become emboldened and attack people

• Demand for illegal bushmeat also increases poaching, adding pressure to the hot semi-arid ecosystem

• Plants are overharvested due to their commercial value - baobab tree fruit, African Blackwood for carving, Gum Arabic for chewing gum, etc. 

  • The Gum Arabic tree is an important plant in Sudan, as it supplies 80% of the world's export of gum

  • Gum Arabic is used extensively in pharmaceuticals, food production, and traditional medicine

The impact of human activity on ecosystem processes

Nutrient cycle

• Overgrazing and intensive agriculture are unsustainable

  • They often lead to soil erosion due to a lack of roots binding the soil together

• Desertification is increasing due to poor management of these activities

  • Poor soil conditions make it hard for vegetation to regrow, creating patches of desert-like conditions

• These activities lead to the disruption of the nutrient cycle

  • The lack of vegetation means less litter to biodegrade and add nutrients to the soil

  • Soil erosion removes the top layer of soil, which contains most of the nutrients

Water cycle

• Deforestation removes the trees and leads to a decrease in transpiration

  • Lower levels of transpiration lead to reduced precipitation

• The problem is expected to worsen as climate change alters rainfall patterns

• Uncontrolled fires can occur, which decimate habitats and lead to an imbalance in the ecosystem

• Water is scarce during the dry season, so it requires careful management in its usage (irrigation, domestic use, etc).

• Food webs are disrupted as habitats are destroyed and biodiversity is reduced

The impact of human activity on biodiversity

• Human activity is reducing hot semi-arid grassland biodiversity by destroying habitats and killing wildlife

• Changing land use is also causing fragmentation, which affects grazing animals and predators that need large areas to roam

• The presence of livestock, such as goats, reduces the amount of vegetation and available water for wild grazing animals

  • Domestic species are replacing wild species in the ecosystem

• Native hot semi-arid grassland species are also threatened by invasive species, e.g. cane toads were introduced in the Australian grasslands as a form of crop pest control, but their population rapidly expanded, putting native species under threat through eating their food and secreting poison when threatened 

•  Conservation and management

• Game reserves have been created in many areas, these:

  • Prohibit local settlements, grazing and farming

  • Strictly control hunting

• This can increase sustainability by allowing the ecosystem to operate without human interference

Management of hot semi-arid grasslands

• Conservation and management of the hot semi-arid grasslands is essential to:

  • Reduce desertification

  • Protect habitats and biodiversity

  • Reduce rural-urban migration

  • Preserve ecosystem processes

How are hot semi-arid grasslands being managed?

Education

• Education including:

  • Sustainable farming methods, including agroforestry and crop rotation, which help to keep the soil healthy

  • Family planning to reduce population growth

Agriculture

• Focus on livestock breeds which are better adapted to drier conditions

• Reduced herd size

• Use high-yielding varieties (HYV)

• Crop rotation

Afforestation

• Tree planting, such as the Great Green Wall across the Sahel, helps to reverse desertification in several ways:

  • The roots help to bind the soil together, reducing soil erosion

  • The canopy offers shade, helping to prevent the soil from drying out and also reducing soil erosion from rainfall landing directly on the soil

  • Nutrients in the soil are replaced by falling leaves and branches

  • The trees increase animal and insect activity, which helps improve soil quality

Fertilisers, high-yield varieties (HYV) and genetically modified (GM) crops 

• Fertilisers, HYV and GM crops can:

  • Increase the yield

  • Reduce the amount of land cultivated

• HYV and GM crops may also be:

  • Drought resistant

  • Pest resistant

Magic stones and terraces

• These help to reduce soil erosion by:

  • Preventing the soil from being blown or washed away

  • Increasing infiltration of water and reducing overland flow

  • Ensuring that dead organic matter stays in one place and can decompose, adding nutrients to the soil