Edexcel GCSE Geography B (1GB0) — Forests Under Threat
Every time you use a piece of paper or turn on a light, you might be connected to the destruction of the world's largest land biome. The taiga faces severe pressure from human activities, which can be categorised into direct and indirect threats.
Direct threats involve the immediate removal of forest cover. The taiga is the world’s primary source of softwood, which is heavily logged for pulp, paper, and construction. The scale is staggering: between 2000 and 2013, taiga tree loss was 1.5 times greater than in the Amazon rainforest, with 12 million hectares cleared in Siberia in 2014 alone. Up to 50% of logging in the Russian Far East is illegal, meaning no replanting occurs, leading to permanent habitat destruction for endangered species like the Amur Tiger (only 450 remain).
Indirect threats are the damaging side effects of industrial activities. Mining for gold and iron ore pollutes water with toxic tailings. Fossil fuel exploitation is similarly destructive: Russia spills roughly 5 million barrels of oil annually from leaky pipelines. In Canada, extracting unconventional oil from tar sands requires 2.4 to 5 barrels of freshwater per barrel of oil, creating toxic tailing ponds that leak into the Athabasca River. Additionally, over 625 large hydroelectric dams in Canada flood vast forest areas and block migratory routes for keystone species like salmon.
When evaluating these threats, direct logging affects the greatest total land area and causes immediate, visible deforestation. However, indirect threats from mining and energy exploitation pose a more severe long-term risk to ecosystem recovery. Because the taiga's cold climate causes incredibly slow decomposition rates, oil and toxic spills persist in the soil for decades, actively poisoning the ecosystem and making natural regeneration nearly impossible.
Rain is usually a lifeline for forests, but atmospheric pollution can turn this vital resource toxic. Acid precipitation occurs when the burning of fossil fuels releases sulphur dioxide () and nitrogen oxides (). These gases react with water vapour in the atmosphere to form weak sulphuric and nitric acids, falling as rain, snow, or fog with a pH lower than 5.7.
This acidity directly damages the waxy cuticle that protects conifer needles. Once the cuticle is compromised, the needles turn brown and fall off, severely reducing the tree's ability to photosynthesise.
In the soil, acid rain causes the leaching of essential nutrients like calcium and magnesium, washing them out of reach of tree roots. Furthermore, the increased acidity mobilises toxic aluminium in the soil, which destroys fine root systems and stops water absorption. Because taiga soils are naturally thin and acidic, they have a very low buffering capacity, meaning they cannot neutralise this added acid. Weakened trees eventually die or succumb to pests, reducing habitats and lowering overall biodiversity.
A tiny insect no bigger than a grain of rice can take down a towering pine tree, especially when the climate tips in its favour. Warmer global temperatures are allowing pests to survive the harsh taiga winters. For example, the spruce bark beetle is shifting from a one-generation lifecycle to bivoltinism (two generations per year) in Scandinavia and Alaska, devastating 1.1 million acres of Alaskan forest.
Pests mechanically destroy trees through girdling, where they bore into the bark and consume the living cambium layer, cutting off the flow of nutrients. They also introduce blue stain fungi that block the tree's vascular system. In Siberia, the Siberian silkmoth defoliates trees, preventing photosynthesis, and recently destroyed over 800,000 hectares of dark taiga.
Fungal diseases add to the destruction. Armillaria root disease spreads underground via cord-like rhizomorphs, causing sapwood decay that makes trees vulnerable to wind throw. Western gall rust produces woody swellings called galls that snap trunks. The loss of dominant trees like the Scots pine triggers a bottom-up collapse of the food web, eliminating habitats and food for insects, voles, and birds.
While natural fires can help regenerate a forest by clearing dead vegetation, climate change has turned them into an abnormally frequent and destructive force. Warmer, drier summers have drastically increased the intensity and size of wildfires, often ignited by lightning strikes. The taiga is highly flammable due to its high tree resin content and thick pine needle litter.
Frequent fires prevent the forest from having adequate recovery time to mature and produce seeds. This high-intensity burning strongly favours fire-tolerant species, which outcompete other plants and reduce the overall variety of plant life. The loss of diverse conifers removes essential food sources, like pine cones, which starves small mammals and impacts apex predators like lynx and owls.
Crucially, fires destroy the organic litter store on the forest floor. Because natural decomposition in the taiga is extremely slow, the litter holds the vast majority of the ecosystem's nutrients. Burning this layer leads to immediate soil erosion and massive nutrient loss, leaving surviving trees weakened and highly susceptible to secondary attacks from pests like the silkworm.
Students often evaluate direct and indirect threats by only listing their impacts. To access top marks in 'Assess' or 'Evaluate' questions, you must provide a balanced judgement comparing their severity—such as noting that logging covers a larger area, but oil spills cause longer-lasting toxic damage due to slow decomposition rates.
In 4-mark 'Explain' questions about acid precipitation, examiners expect a step-by-step causal chain: identify the specific gases (SO₂ or NOₓ), describe the leaching of nutrients or cuticle damage, explain how this weakens the tree, and state how it ultimately reduces biodiversity.
Always use specific scientific terminology like 'leaching' for soil nutrient loss and 'cuticle' for needle damage rather than generic phrases like 'washes away' or 'damages leaves'.
Link forest fires directly to the nutrient cycle. Remember that because decomposition in the taiga is incredibly slow, most nutrients are stored in the litter; when fires destroy this store, the ecosystem's ability to recover plummets.
Direct threat
An activity that immediately removes or destroys the forest cover, such as commercial logging for timber.
Indirect threat
Damage caused by the side effects of industrial activity, such as oil spills, acid rain, or habitat fragmentation.
Softwood
Timber from fast-growing coniferous trees (e.g., pine, spruce) that is primarily used for paper pulp and construction.
Tar sands
Unconventional petroleum deposits containing bitumen, requiring massive amounts of water and open-pit mining to extract.
Keystone species
A species, such as salmon or the Scots pine, that has a disproportionately large impact on its ecosystem and food web.
Acid precipitation
Rain, snow, or fog that has a pH lower than 5.7 due to atmospheric pollution from sulphur dioxide and nitrogen oxides.
Cuticle
The protective, waxy coating on conifer needles that is easily damaged by acid rain.
Leaching
The process by which essential nutrients (like calcium and magnesium) are washed out of the soil by water or acid rain.
Buffering capacity
The ability of a soil to naturally neutralise added acids; this is notably low in thin taiga soils.
Bivoltinism
The completion of two reproductive cycles within a single year, increasingly common in taiga pests due to warmer temperatures.
Girdling
The destruction of the layer of living tissue (cambium) beneath the bark by pests or fungi, cutting off the flow of sap and nutrients.
Rhizomorphs
Cord-like fungal strands that grow through the soil to infect the healthy roots of neighbouring trees.
Galls
Woody swellings on a tree trunk or branches caused by fungal infections, which often lead to the trunk breaking.
Fire-tolerant species
Plant species with specific adaptations, such as thick bark, that allow them to survive or rapidly recolonize an area after a wildfire.
Put your knowledge into practice — try past paper questions for Geography B
Direct threat
An activity that immediately removes or destroys the forest cover, such as commercial logging for timber.
Indirect threat
Damage caused by the side effects of industrial activity, such as oil spills, acid rain, or habitat fragmentation.
Softwood
Timber from fast-growing coniferous trees (e.g., pine, spruce) that is primarily used for paper pulp and construction.
Tar sands
Unconventional petroleum deposits containing bitumen, requiring massive amounts of water and open-pit mining to extract.
Keystone species
A species, such as salmon or the Scots pine, that has a disproportionately large impact on its ecosystem and food web.
Acid precipitation
Rain, snow, or fog that has a pH lower than 5.7 due to atmospheric pollution from sulphur dioxide and nitrogen oxides.
Cuticle
The protective, waxy coating on conifer needles that is easily damaged by acid rain.
Leaching
The process by which essential nutrients (like calcium and magnesium) are washed out of the soil by water or acid rain.
Buffering capacity
The ability of a soil to naturally neutralise added acids; this is notably low in thin taiga soils.
Bivoltinism
The completion of two reproductive cycles within a single year, increasingly common in taiga pests due to warmer temperatures.
Girdling
The destruction of the layer of living tissue (cambium) beneath the bark by pests or fungi, cutting off the flow of sap and nutrients.
Rhizomorphs
Cord-like fungal strands that grow through the soil to infect the healthy roots of neighbouring trees.
Galls
Woody swellings on a tree trunk or branches caused by fungal infections, which often lead to the trunk breaking.
Fire-tolerant species
Plant species with specific adaptations, such as thick bark, that allow them to survive or rapidly recolonize an area after a wildfire.
