UK Ecosystems

UK Woodlands

• Did you know that at least $80\%$ of UK woodland is actually less than $100$ years old? Much of it is managed plantation.
• Woodlands cover approximately $12\%$ of the UK land area, distributed in fragmented "pockets" across the country.
• Deciduous woodland is dominant in lowland areas of the South and East of the UK. It features fertile "brown earth" soils and experiences a mild climate (averaging $4^\circ\text{C}$–$17^\circ\text{C}$ with $\sim 1000\text{ mm}$ rainfall). Trees like Oak, Ash, and Beech lose their leaves in winter; these leaves decompose (a biotic process) to keep soils fertile.
• Deciduous woodlands have a distinct vertical structure:
  1. Canopy ($20\text{ m}$–$35\text{ m}$): The tops of the tallest trees, blocking most sunlight.
  2. Sub-canopy: Smaller trees and saplings, like Hazel.
  3. Herb/Field layer: Plants like bluebells and ferns.
  4. Ground layer: Mosses and leaf litter.
• Coniferous woodland dominates northern latitudes and upland areas, such as the Scottish Highlands and Kielder Forest. These environments have thinner, acidic soils, so evergreen trees with needle-like leaves (e.g., Pine, Spruce) thrive here.
• The UK's oldest and rarest woodland is the temperate rainforest, found primarily in North-West Scotland.

Moorlands and Heathlands

• You can find similar heather plants on a freezing Scottish mountain and near the warm southern coast, but the underlying environments are completely different.
• Moorland is found in upland areas typically above $250\text{ m}$ (e.g., the Pennines, Dartmoor, and Cairngorms). Because of the Environmental Lapse Rate, temperatures drop by $\sim 1^\circ\text{C}$ for every $100\text{ m}$ of altitude, restricting plant growth.
• Moorlands experience high rainfall ($>1250\text{ mm/year}$) and strong winds. The soils are waterlogged, acidic, and nutrient-poor, forming peat bogs. Human management, like sheep grazing and burning, prevents natural succession (the growth of trees from seeds).
• Heathland is distributed across lowland areas ($<300\text{ m}$) in the southern UK, such as the New Forest and Surrey Heaths. It occurs on porous, sandy soils.
• Heathland soils are acidic and infertile due to leaching, a process where rainwater washes essential nutrients out of the soil. Despite this, heathlands are critical habitats for rare species like the nightjar and sand lizard.

Wetlands

• When rivers overflow their banks, they don't just cause floods—they create some of the richest natural habitats in the country.
• Wetland ecosystems are distributed across low-lying areas and floodplains, such as the Somerset Levels, Norfolk Broads, and the River Severn.
• They are defined by permanently or seasonally waterlogged soils that are anaerobic (oxygen-poor). Despite lacking oxygen in the soil, floodplain wetlands are extremely fertile.
• Wetlands support hydrophytic (water-loving) vegetation like reeds, bulrushes, and water lilies, alongside fauna such as otters, water voles, and wading birds (e.g., snipe).

Calculating Ecosystem Distribution

• In exams, you may be asked to calculate the percentage area of an ecosystem using provided figures.

• Formula: $(\text{Ecosystem Area} \div \text{Total Area}) \times 100$

• Step 1: Identify your values. For example, if Scotland has $1.5\text{ million}$ hectares of woodland out of a UK total of $3.2\text{ million}$ hectares.

• Step 2: Substitute into the formula: $(1.5 \div 3.2) \times 100$

• Step 3: Calculate the final percentage: $46.875\%$ (which rounds to $46.9\%$).

The Value of UK Marine Ecosystems

• The seas around the UK are a natural asset valued at approximately $£211\text{ billion}$.
• Marine ecosystems provide essential ecosystem services (benefits to humans). These are split into provisioning (food/fuel), regulating (climate/flood protection), and cultural (tourism) services.
• Economically, the UK fishing fleet is the 7th largest in the EU, providing $\sim 12,000$ jobs on boats, while sea angling alone contributes $£1.5\text{ billion}$ annually. For energy, North Sea oil and gas reserves (estimated at $24\text{ billion}$ barrels) support $450,000$ jobs. The sea is also vital for renewables, hosting massive projects like the London Array wind farm ($175$ turbines). For cultural services, marine tourism attracts $250\text{ million}$ visitors annually, contributing $£3\text{ billion}$ to the economy and supporting $200,000$ jobs.
• Environmentally, marine ecosystems are crucial for regulating the climate and providing coastal protection. Saltmarshes act as natural defences against flooding and erosion. Furthermore, saltmarshes and seagrass beds store $136\text{ megatonnes}$ of carbon and capture an additional $620,000\text{ tonnes}$ every year.

Human Degradation of Marine Ecosystems

• Human activities are putting unprecedented pressure on our seas, altering food webs, destroying habitats, and significantly reducing marine biodiversity.
• Overfishing removes top predators and disrupts food chains. For example, the North Sea cod stock collapse in 2011 demonstrated how intense commercial fishing (where just $4\%$ of the fleet takes $50\%$ of the catch) can devastate populations.
• Eutrophication is a process that destroys marine life through pollution:
  1. First, nutrient runoff from farm fertilisers or sewage enters the sea.
  2. This sudden nutrient spike causes a rapid algal bloom.
  3. The thick layer of algae blocks sunlight from reaching bottom-dwelling plants.
  4. When the algae die, they sink and are decomposed by bacteria.
  5. The bacteria multiply and use up the dissolved oxygen in the water, causing hypoxia (severe oxygen depletion), which suffocates and kills fish.
• Climate change is also degrading ecosystems. Warming seas have forced cold-water plankton to shift $1000\text{ km}$ north, while warm-water species like tuna move into UK waters. Furthermore, invasive species like wireweed (from the Pacific) out-compete native kelp habitats, further threatening native biodiversity. Finally, dredging (mechanical removal of sediment) directly destroys the seabed.