Paper 3 Section B - Forests under threat

Give reasons why forest biomes are very important ecosystems on Earth

• Absorb and store huge levels of carbon

• Release oxygen into the atmosphere

• Regulate the hydrological cycle

  • Interception

    • Less surface runoff, prevents flooding and soil erosion

  • Transpiration

    • Releases water vapour into the atmosphere

  • Infiltration

    • Plant roots increase infiltration, increases groundwater supplies and reduces surface runoff

• Provide habitats

Describe the relationship between biotic and abiotic characteristics in forest biomes

The biotic and abiotic characteristics are interdependent; they interact with and influence each other

Give examples of the interdependence of abiotic and biotic characteristics of the tropical rainforest

Climate, soil, water, plants, animals and humans

• Climate and plants are interdependent

  • Warm wet climates allow plants to grow quickly

  • Plants absorb sunlight for photosynthesis

  • As there are so many trees in the ecosystem, transpiration is high; the majority of transpired water vapour goes straight back into the clouds above the rainforest, causing rain

• Plants and animals are interdependent

  • Plants provide food and shelter, allowing a large amount of biodiversity

  • Biodiverse plant and animal life means there is a large amount of organic matter releasing nutrients into soil

• Humans are interdependent with plants and animals

  • Humans can grow food

  • Humans can hunt for animals

  • Plants have many medicinal uses

  • Traditional agriculture methods ensure that nutrients are not depleted from topsoil

• Animals and soil are interdependent

  • Decomposers break down organic material releasing nutrients into the soil

etc….

Describe the different layers of the tropical rainforest

In the tropical rainforest, plants grow in distinct layers because they compete for sunlight; each layer has different conditions and types of organisms

• Emergent layer

  • Very tall trees due to competition for sunlight

  • Receive the most sunlight, allowing rapid growth

  • Poke out of the main canopy layer

  • Straight trunks

  • Buttress roots that support their weight and prevent them from falling

• Canopy

  • Forms a dense roof of leaves that blocks most sunlight from reaching other layers

  • Many epiphytes and lianas

  • Insects, birds, snakes, monkeys, sloths

• Under canopy

  • Made of younger trees that have yet to reach their full height

  • Cooler and shady with limited sunlight, so plants grow large leaves to maximise surface area

  • Lianas grow from the ground and climb trees

  • Insects, reptiles, mammals

• Forest floor/ shrub layer

  • Very dark

  • Shrubs have large, broad leaves

  • Insects, fungi, decomposers

  • Covered by shallow humus (dead decaying leaves and roots)

Describe how plants are adapted to the tropical rainforest climate

• Stratified layers

  • Reduces competition as it creates layers with different environmental conditions, so plants in each layer are adapted differently to the conditions in their layers; this means that plants are only competing with other plants in their layer

    • Eg. In the shrub layer and under canopy, plants have large leaves to maximise surface area to absorb as much sunlight as possible, whereas in the emergent layer trees have large buttress roots

• Large leaves in undercanopy and shrub layer

• Buttress roots

  • Supports the weight of tall trees, keeping them stable in thin, nutrient poor soil

  • The shallow root system allows the plant to quickly absorb nutrients from the surface before they are washed away by heavy rain (leaching)

• Drip tips

  • Allow water to flow off the leaf so they don’t stay too wet, preventing rotting, fungal growth and damage from weight

• Epiphytes →canopy

  • Plants that grow on the surface of other taller plants, allowing them to escape the dark forest floor and access abundant light for photosynthesis

• Lianas (woody vines) →canopy into emergent

  • Lianas are woody vines that climb trees to reach more sunlight without using energy to grow a large trunk

• Straight trunks (emergent layer)

  • Growing tall and straight allows trees to reach the emergent layer more quickly to reach the most light, without wasting energy on side branches as there is limited light in the undercanopy

Describe how animals are adapted to the tropical rainforest climate

• Camouflage

  • Help them blend into the environment to prevent being seen and eaten by predators

• Poisons and venoms

  • Can paralyse or kill predators before they are eaten

• Long limbs, strong tails, strong claws

  • Allows animals to climb trees and grasp branches

• Large eyes

  • Adapted to the low light levels of the forest floor, improving vision to hunt prey or search for food

• Birds have strong beaks to break open nuts

• Birds have loud calls to hear each other through thick vegetation

What is the rate of nutrient cycling in the tropical rainforest like?

Very quick nutrient cycle in the tropical rainforest

• This means that there are always plenty of nutrients available for plants and animals to use, supporting high levels of biodiversity

Describe the nutrient stores and transfers of the tropical rainforest (biomass, litter, soil)

Why are there high rates of nutrient cycling?

Stores:

• Very large biomass store

  • Rapid rates of growth (rapid photosynthesis due to sunlight and precipitation)

• Small litter store

  • Rapid decomposition (high temperatures, moist)

• Small soil store

  • Loss of nutrients due to leaching

  • Increase nutrients due to precipitation and weathering

Transfers:

• Large take up of nutrients

  • due to rapid plant growth

• Large supply of nutrients

  • Weathering and precipitation

• Large loss of nutrients

  • Leaching

High temperatures and moist so high rates of decomposition

High photosynthesis, so much growth and uptake

Define biodiversity

Number/ variety of different plant and animal species

Why does the tropical rainforest have high biodiversity?

• Stratified layers

  • allows many varying conditions on each layer and therefore many different habitats; plants and animals become highly specialised to their different environments, so lots of different species develop over years

• Rainforests have stable climates and don’t have seasons

  • so plants and animals don’t have to cope with changing conditions and there is always plenty of food, allowing many different types of organisms to survive

• Rapid nutrient cycling, which speeds up plant growth and therefore food for organisms

Why does the tropical rainforest have complex food webs?

• High biodiversity and many different species, allowing there to be many different links between organisms

• Some animals can be both primary and secondary consumers

What is the largest biome on earth?

Taiga

Briefly describe the taiga climate

• 50 70 North and South, Russia and Canada

• Seasonal: short, wet Summers and long, cold and dry Winters

• Very short growing season

• Low precipitation

• Many sunlight hours in Summer, but very little in Winter

Describe how plants are adapted to the taiga forest climate

• Cone shaped leaves

  • Allows snow to slide off, rather than collect and weigh down trees, snapping branches; branches are also flexible

• Needles + waxy cuticle

  • Reduces the surface area of the leaf, reducing water loss

• Flexible branches

  • Can bend if snow goes on it

• Simple structure (compared to tropical rainforests)

  • Maximises light absorption; adaptation to poor growing conditions as a simple structure requires fewer nutrients/ less sunlight/water than a dense stratified system

• Evergreen trees

  • Allowing them to maximise photosynthesis when there is available light

Describe how animals are adapted to the taiga forest climate

• Migratory

  • Enables them to escape extremely cold winters and scarcity of food

• Thick, oily fur

  • Insulates them, preventing them from losing body heat in the cold

• Hibernate

  • Allows them to conserve energy when food is scarce

• Camouflage

  • Hide from predators and prey

• Oversized feet (compared to body size)

  • Exceptionally large feet compared to body size, preventing them from sinking into soft snow, allowing them to escape predators and to chase prey

Describe the nutrient stores and transfers of the tropical rainforest (biomass, litter, soil)

Why are there high rates of nutrient cycling?

Smaller stores and smaller flows of transfer due to slow rates of growth and decomposition (cold, low precipitation)

• Small biomass store

  • Plants can only grow for a few months of the year

• Largest store is litter store

  • Very slow rates of decomposition

• Small soil store

  • Low precipitation,

  • Slower weathering

• Plant nutrient uptake is very low

  • Low biodiversity, slow growth (low photosynthesis)

• Low nutrient supply

  • Low precipitation so fewer nutrients are added through dissolved rainwater or through weathering

• Some nutrient loss

  • Through leaching after snowmelt in Summer

• Slow rates of decomposition due to cold, dry climate

• Slow rates of growth due to short growing season — mainly cold, low precipitation and limited sunlight

What is meant by the productivity of a forest?

The rate at which plants generate new biomass through photosynthesis

Why does the taiga forest have much lower levels of biodiversity compared to the tropical rainforest?

• Land was much colder and covered by ice until around 15,000 years ago, so species have had relatively little time to adapt to the current climate

  • As it emerged from last major ice age

• Taiga forests have a simpler structure, so there aren’t many different habitats so there are fewer ecological niches

• Taiga forests are much less productive and nutrients take a much longer time to return to soil; growing season is also very short - this means that there’s not much food available, so there is a constant struggle for survival

Name a direct and indirect threat to the tropical rainforest

• Direct: deforestation

• Indirect: climate change

Give some indirect threats to the tropical rainforest

Main threat: climate change

• Pollution

  • Water pollution: toxic chemicals poison organisms, pesticides and insecticides kill pollinators

  • Air pollution: acidic gases cause acid rain, impacts soil pH and tree roots

• Invasive species

  • From the global spread of goods and products around the world; creates competition and disrupts ecology

Define ecosystem stress

• Ecosystem stress is when an ecosystem is put under pressure

• by changes or disturbances

• that disrupt its normal functioning, balance and stability

Describe the causes of deforestation in the tropical rainforest (7)

Agriculture:

• Commercial agriculture

  • Cleared for cattle grazing

  • Cleared for plantations (palm oil, soya)

• Subsistence agriculture — poverty

  • Farmers grow food for themselves and their family

Forestry:

• Commercial hardwood logging

  • Trees are felled to make furniture, for construction

• Local demand for fuelwood — poverty

  • Burnt and used as a fuel for cooking

Energy and infrastructure:

• Demand for biofuels

  • Large amounts of land is cleared to grow crops for biofuels (as conditions are good for photosynthesis)

• Hydroelectric power

  • Rainforests have large rivers, so rivers are flooded and dams are built to generate electricity

    • Destroys habitats and displaces communities

• Roads

Demand for mineral resources:

• Minerals in rainforest are extracted by mining and drilling

  • Roads must be built to transport these

What are the underlying root causes of deforestation in the rainforest? (4)

• Poverty

  • Local people cannot afford food, so clear the forest for subsistence farming

  • Cannot afford fuel, so cut down trees for fuelwood for cooking

• Debts

  • Exploit the forest by selling cash crops and exporting timber to pay off debts

• Development

  • Demand for energy: HEP, biofuel, coal

• Increasing affluence globally, increased demand for products that require raw materials

  • Minerals

  • Timber

Describe the environmental impacts of deforestation (4)

• Soil erosion and landslides

  • No tree roots to give structure and hold it together

• Soil becomes less nutrient dense

  • Leaching increases due to no interception

• Global warming

  • Less CO2 absorbed

  • Burning releases CO2

• Reduction in biodiversity

  • Cannot live in or adapt fast enough to new conditions

Explain why climate change is an indirect threat to the health of tropical rainforests (6)

Causes drought

• Drought kills decomposers

  • Alters the nutrient cycle

• Drought leads to forest fires

  • Destroys vegetation

• Drought leads to ecosystem stress

  • Extinction as cannot survive

• Aquatic habitats like streams and rivers dry up

  • meaning that aquatic organisms die

• Lack of water can cause the leaves and fruits of tree to die and fall off

  • reducing food supply in the canopy and affecting food webs

• Drying litter reduces decomposition

  • Fewer nutrients released back into the soil, plants grow less

Describe the direct threats to the taiga forest (causes of deforestation) (5)

Direct (damages forest straight away at the source):

Taiga is made up of softwood

• Logging for softwood

  • Used in construction and for furniture

• Pulp and paper production

  • Paper comes from the softwoods (coniferous) trees in the taiga; the trees are felled and mashed into a pulp to be used to make paper

• Exploitation of minerals

  • The taiga forest is rich in minerals; trees are felled to make space for mines and for roads

• Extraction of oil and gas (and tar sands)

  • Open pit mining requires deforestation

  • Land deforested for roads and pipelines

• Flooding of rivers and building of dams for HEP

  • Destroys habitats

Describe the indirect threats to the taiga forest (4)

Indirect (harms the forest through another process):

• Climate change

  • Softwoods are flammable, vulnerable to wildfires

    • Wildfires also increase the dominance of fire-tolerant species, reducing biodiversity

  • Animals and plants will die out, loss of biodiversity

  • Proliferation of pests and pathogens effect species

• Exploitation of minerals

  • Harmful chemicals from mining are washed into the river ecosystems, disrupting the wildlife

• Exploitation of fossil fuels

  • Tar sands - open pit mining

    • Extraction of oil in tar sands produces toxic waste and uses huge amounts of water

• Hydroelectric power to generate electricity

  • Disrupts fish migration patterns, preventing fish from reaching breeding grounds, which can reduce the fish populations

  • Altered water levels affect soil moisture, which affects which plants can grow

What natural threats contribute to a loss of biodiversity in the taiga forest (3)

• Acid precipitation from sulfur dioxide from burning fossil fuels

  • Can make soils too acidic to support growth

  • Can kill aquatic organisms in lakes and streams if it lowers the pH of natural water sources

  • Damages plants’ leaves and weakens the trees, reducing photosynthesis

• Increasing frequency of forest fires (hot, dry summers increase susceptibility)

  • The taiga forest is naturally adapted to wildfires as they allow new growth and regenerate the forest; however climate change is increasing the frequency of the fires

    • No time for regeneration, so less tolerant species go extinct, affecting animals that eat them

    • Fire tolerant vegetation becomes dominant, loss of biodiversity

• Proliferation of pests + diseases

  • Reduce biodiversity by killing large numbers of trees

    • Taiga’s low biodiversity mean that trees of same species live very close together, so a disease can destroy a large area rapidly

    • Warming caused by climate change is making it easier for pests and pathogens to survive

Name the global actions designed to protect tropical rainforest species and areas

• CITES

• REDD

Describe CITES and give its advantages and disadvantages

Tropical rainforest global action:

CITES (convention on international trade in endangered species of wild fauna and flora)

• Agreement to tightly control trade in wild animals and plants

Advantages:

• Many countries are apart of the agreement (180+)

  • Tackles issue at global level, controlled worldwide

• Encourages sharing of information about wildlife trade

  • which raises awareness of threats to biodiversity

• Protects endangered species by controlling or banning international trade

  • preventing extinction and protecting biodiversity

• Reduced ivory (elephant horn) trade

Disadvantages:

• Protecting species does not prevent global warming and deforestation

  • they could still go extinct if habitats are destroyed

• Not all countries are members

  • so does not control all international trade

• Each country is in control of their own management and laws

  • so they could break their own rules without consequence

• Low income countries may not have the finances to implement management strategies

• Species must be actively under threat to be protected

Describe REDD and give its advantages and disadvantages

Tropical rainforest global action:

REDD (reduced emissions from deforestation and forest degradation)

• Scheme that offers financial incentives to forest owners in poorer countries for not deforesting

Advantages:

• Cheap approach of reducing emissions as no implementation or development of new technologies

• Deals with the cause of climate change as well as direct impacts of deforestation

• The forest is protected, so it remains a habitat for species - biodiversity is not lost

• Countries are more likely to conserve their forests for financial rewards, as opposed to doing it for just the environmental benefits

• Financially supports local communities and governments that are dependent on forest resources for survival and financially

Disadvantages:

• Very difficult to police, so illegal deforestation may continue in other areas

• Preventing forest activities (eg. mining, agriculture) may affect local communities who depend on the income from them - money goes to government

• Aspects of REDD are not clear, meaning that it may be possible to cut down rainforests but still receive rewards if they are replaced with other types of forest (eg. replaced with palm oil plantations which are lower in biodiversity)

Explain why rates of deforestation vary globally in the tropical rainforest: (4)

• Increasing rates

Increasing rates:

• Poverty

  • Increases the number of small-scale subsistence farming (as market prices are expensive) and use of fuel wood (other fuels are expensive)

• Foreign debt

  • Huge market for goods from tropical rainforests, so it is easy for poor countries to make money to pay back debt they owe — cash crops

• Economic development

  • Low income countries do not have the money to invest in forest conservation and management

  • Newly industrialised countries have high demand for resources from tropical forests (eg. timber for manufacturing, energy resources)

• Conflict and war

  • Funding and efforts will be focused on other needs

Explain why rates of deforestation vary globally in the tropical rainforest: (4)

• Decreasing rates

Decreasing rates:

• Government policies and laws

  • Fines and prosecution for illegal deforestation

• International condemnation

  • Puts pressure on companies involved in deforestation, shaming them and discouraging consumers from buying products

• National parks + conservation areas

  • Use of national park status enforces protection and conservation

• Education and public awareness

  • Encourages donations, support and public pressure for forest protection

Describe methods of sustainable tropical rainforest management (4)

Sustainable forestry involves considering the environmental, social and economic aspects of forest management — alternative livelihoods

• Ecotourism

  • Small-scale tourism that protects the environment and benefits local people

    • Provides jobs without cutting trees

    • Raises awareness and educates tourists of rainforest value

    • Profits can fund conservation projects

Sustainable farming:

• Agroforestry:

  • Trees and crops are planted at the same time next to each other, mimicking the natural forest structure

    • Maintains biodiversity

    • Trees protect soil from erosion, keeping the land productive and thus reducing the need to repeatedly clear new forest land

    • Less trees cut down

• Crop rotation

  • Growing different crops on the same area of land over a planned sequence over several years

    • Maintains soil nutrients because different plants use different nutrients, reducing the need to deforest new, fertile land

• Afforestation

  • Trees are replanted after they are cut down

Name the methods of conserving taiga forests

• Creating national parks

• Creating wilderness areas

• Sustainable forestry

Describe the advantages of creating national parks in the taiga forest and its challenges

National parks: an area that is mostly in its natural state that is managed to protect biodiversity and promote recreation

Advantages:

• Allows tourists and recreational users to access, bringing income

• Prevents unsustainable human activity (destruction of habitats)

• Protects species and habitats

• Raises awareness and educates people on the importance of protecting the forest

Disadvantages:

• May not take into account the needs of indigenous communities who may use the land for hunting

• Access roads, infrastructure and pollution from tourists may harm the ecosystem

• Money and resources are needed to build

Describe the advantages of creating wilderness areas in the taiga forest and its challenges

Wilderness area: an area that is undisturbed by human activity, managed with the aim of protecting the landscape

Advantages:

• Highest level of protection as most human activity is banned

• Usually covers a very large area so large scale processes (eg. migrations) can still occur

• Help to prevent climate change; stabilise local climates and store carbon

Disadvantages:

• Large, remote areas are hard to police

• Can cause a loss in gdp if mining and logging cannot occur

• Economic pressure from companies and tourists who want to build roads or use resources

Describe the sustainable forestry in the taiga forest and its challenges (2)

Sustainable forestry: ways of harvesting the timber from the forest without damaging it in the long term

• Limit number of trees that can be cut down (selective logging — only large valuable)

  • Reduces deforestation and habitat destruction

• Companies may be required to regenerate the area and replant trees after logging

  • Allows economic benefits while still conserving the environment

Disadvantages:

• Some countries may struggle to enforce restrictions

• Restrictions may be unclear, allowing people to bypass the rules and continue to exploit the forest

• Different groups may disagree with the rules and restrictions, causing conflict

• Money and resources are needed to regenerate and replant, reducing profits

• Roads are often built to transport

  • Fragment habitats

  • Pollution from vehicles

• Animals can be harmed during deforestation and disturbed by the noise

Give reasons for protecting or exploiting forest and natural resources in the taiga (5p, 3e)

Protection:

• Scientists: Prevents global warming

  • Reducing carbon stores

• Environmentalists: Prevent extinction of species — ecology disruption and loss of biodiversity

  • Uniquely adapted, so will be unable to live elsewhere

• Indigenous peoples: Many indigenous people depend on the forest for services and goods so that they can live their traditional way of life

• Local residents: Taiga is culturally important to them and want to conserve heritage

• Economists: Tourists may want to visit the forest and enjoy the natural environment

  • Brings income

Exploitation:

• Residents: Forest industries provide lots of jobs and employment

• Businesses: Exploitation of the forest generates lots of wealth for oil companies and logging companies

• Governments sell exploited resources, generating income