Sustaining Ecosystems

🔍 Why Ecosystems Are Under Threat — The Cause Chain

Figure 1: The nutrient cycle. Sustainable management must keep this cycle intact.

Ecosystems do not collapse all at once. They unravel gradually, under pressure from several directions at the same time. Understanding the pressures matters because different management strategies address different ones — and an answer that simply says "deforestation is bad" without explaining the mechanism will never reach the top mark band.

Here is what the pressures look like in practice, and how they connect:

⚙️ What Are Ecosystem Services? — Why This Matters for People

Here is an analogy that might change how you think about this. Your local council maintains the road outside your house. The water company treats the water before it comes out of your tap. The Environment Agency manages flood defences. All of this costs money. But ecosystems do equivalent jobs — for free. When a wetland filters pollutants from river water, that is a service worth billions of pounds. When a tropical rainforest absorbs CO₂ from the atmosphere, it is doing the job that carbon capture technology does, except without the cost. When mangrove forests line a coastline, they absorb the energy of storm waves, protecting coastal communities from flooding.

Ecologists call these ecosystem services, and they divide them into four categories:

The total economic value of all ecosystem services globally has been estimated at approximately $125–145 trillion per year — roughly 1.5 times the entire world GDP. This is not a precise calculation, but it makes the point: when ecosystems are damaged, the cost is not just environmental. It is economic.

🌊 Case Study A: Great Barrier Reef Marine Park, Australia (HIC)

The Great Barrier Reef stretches for 2,300 kilometres along the coast of Queensland, north-eastern Australia. It is the world's largest coral reef system — home to 1,500 species of fish, 4,000 types of mollusc, 240 species of birds, and six of the world's seven species of marine turtle. In 1981, UNESCO designated it a World Heritage Site. In 2016, its coral began to die in the largest bleaching event ever recorded.

The Threats

• Coral bleaching from ocean warming: In 2016 and 2017, back-to-back mass bleaching events killed approximately 50% of the reef's shallow-water coral. Bleaching occurs when ocean temperatures rise just 1–2°C above the summer maximum: the coral ejects the algae (zooxanthellae) living in its tissue, turns white, and — if temperatures remain elevated — starves and dies. The 2016 event was directly linked to climate change compounded by an El Niño warming event.
• Water quality from agricultural run-off: Sugar cane and cattle farming in Queensland's coastal hinterland generates run-off containing sediment, nitrogen fertilisers and pesticides. This reduces water clarity (limiting the sunlight coral needs for photosynthesis), stimulates algae blooms that suffocate coral, and introduces pesticides toxic to coral larvae.
• Crown-of-thorns starfish: This large, coral-eating starfish undergoes population explosions — partly triggered by excess nitrogen in the water — that can destroy large areas of reef. A single outbreak of crown-of-thorns can reduce coral cover by 90% in an affected area.
• Tourism damage: 25 million tourist visits per year bring boats, divers, and physical disturbance. Anchors damage coral directly; sunscreen chemicals have been found to inhibit coral larvae development; some operators have historically allowed tourists to stand on or touch coral.

The Management Response

The Great Barrier Reef Marine Park Authority (GBRMPA) was established in 1975 and manages the reef under a comprehensive zoning system. The 344,400 km² park is divided into eight zones with different permitted activities:

• Preservation zones (least disturbed areas): no entry permitted except for scientific research with special permission
• Marine national park zones: no fishing, no collecting — snorkelling, diving and boating permitted
• Habitat protection zones: some fishing and collecting permitted under licence
• General use zones: most activities permitted including commercial fishing

In 2004, the no-take zones were expanded from covering 4.5% of the park to 33% — one of the largest marine protected area expansions in history. Studies have found that fish biomass inside no-take zones is 50–60% higher than in comparable fished areas.

The Reef 2050 Water Quality Improvement Plan aims to reduce agricultural run-off by 50% by 2025, using financial incentives for farmers to adopt lower-impact practices (reduced fertiliser use, vegetated riparian buffers along waterways). Coral restoration programmes breed heat-resistant coral varieties in nurseries and transplant them onto bleached sections of reef.

Evaluation: Effective — But Fighting the Wrong Battle?

🌳 Case Study B: REDD+ in the Congo Basin, DRC (LIC)

The Democratic Republic of Congo contains the world's second-largest tropical rainforest after the Amazon — approximately 1.5 million km² of forest covering most of the country. It is home to gorillas, chimpanzees, forest elephants, and an extraordinary diversity of plant species. It is also one of the world's most important carbon sinks: the Congo Basin forest stores approximately 30 billion tonnes of carbon — equivalent to three years of global CO₂ emissions. And it is being destroyed, slowly but relentlessly, mostly by the country's own people — not out of greed, but out of need.

The Threat: Poverty-Driven Deforestation

Approximately 90% of the DRC's population relies on charcoal for cooking fuel. There is almost no alternative. The electricity grid reaches perhaps 9% of the population. Solar cooking technology is expensive. Wood is free in the forest. So trees are cut, converted to charcoal in earth kilns (an inefficient process that loses about 75% of the wood's energy), and sold in cities where 12 million people need to cook their food. Subsistence farming also drives deforestation: families clear small patches of forest to grow cassava and maize. When the thin tropical soil becomes exhausted after 2–3 years, they clear more.

The tragedy is that the DRC's forest is priceless to the global climate — but has almost no economic value to the people living next to it if it is left standing. A tree only has value once it is cut down. This is the fundamental problem that any management approach must solve.

The REDD+ Approach

REDD+ stands for Reducing Emissions from Deforestation and forest Degradation. The core idea is simple and powerful: rich countries that have already cut down most of their own forests, and whose CO₂ emissions are causing global warming, pay developing countries to protect their forests instead of clearing them. The protected forest generates carbon credits — each credit represents one tonne of CO₂ stored — which are traded on international carbon markets or bought by governments as part of their climate commitments.

• Protected areas cover approximately 15% of the DRC's territory — but enforcement is extremely difficult in a country larger than Western Europe with very limited government capacity
• Norway has paid DRC over $150 million under REDD+ agreements to protect specific areas of forest
• In principle, REDD+ should provide a revenue stream that makes standing forest economically competitive with charcoal production or farming
• In practice, payments have often failed to reach local communities — corruption, weak governance and complex payment chains mean the money sometimes stops at the national level
• Local communities who are told they can no longer cut trees for charcoal but receive no economic alternative are understandably hostile to conservation

Evaluation: The Right Idea, The Wrong Execution?

🦋 Case Study C: Rewilding at Knepp Estate, West Sussex, UK (HIC)

In 2001, Charlie Burrell and Isabella Tree made a decision that their neighbours thought was eccentric bordering on insane. They owned 3,500 acres of fertile farmland in the Weald of West Sussex — and they decided to stop farming it.

Not because the land was unproductive. Because intensive farming had made it biologically dead. Decades of ploughing, fertilisers, pesticides and tight grazing management had produced good yields of wheat and oilseed — but the hedgerows were empty, the ponds were silted, the soil was compacted, and the fields were silent. There were no turtle doves. No nightingales. No purple emperor butterflies. No stag beetles. The land produced food but nothing else.

What happened next became one of the most celebrated experiments in modern conservation — and a case study that examiners love because it is genuinely surprising.

The Rewilding Approach

Rewilding means removing intensive human management and allowing natural processes to reassert themselves. At Knepp, this meant:

• Stopping all ploughing, pesticide use, and intensive grazing
• Introducing free-roaming large herbivores to mimic the natural grazing patterns of pre-agricultural Britain: longhorn cattle, Tamworth pigs, Exmoor ponies, and fallow deer — all of which create different habitats through their feeding and movement
• Allowing natural scrub and woodland to develop wherever it chose, without human direction
• Creating new ponds, allowing rivers to meander naturally, and removing drainage infrastructure
• No introduction of specific plants or tree species — the emphasis was on letting nature decide what grew where

The Results — Twenty Years Later

• Turtle doves — critically endangered in the UK, with numbers down 98% since 1970 — now breed at Knepp. It hosts approximately 2–3% of the entire UK population.
• Nightingales — one of Britain's most threatened species — have 20+ breeding pairs, more than anywhere else in the UK
• Purple emperor butterflies — Britain's largest butterfly, rare elsewhere — appear in their hundreds in summer
• White storks nested at Knepp in 2020 — the first successful white stork nesting in Britain for over 600 years
• All five UK species of owl are present; peregrine falcons, hobbies and red kites breed regularly
• Massive recovery in insect abundance — critical for pollination and the food chain
• Soil carbon levels have increased substantially; the land now acts as a carbon sink rather than a carbon source

The Economics

Perhaps the most important lesson from Knepp for geographers: rewilding is not just ecologically successful — it is financially successful. The estate has developed a safari-style tourism business (glamping safaris, guided wildlife walks, educational visits) that generates approximately £2.5 million per year — significantly more than the intensive farming it replaced. The wildland beef and pork from the free-roaming herds sells at premium prices. The book written by Isabella Tree about the project became a bestseller. Wildlife documentaries have been filmed there. The land is now worth more wild than it was farmed.

Evaluation: Brilliant — But Scalable?

⛓️ The Fundamental Tension: Why Conservation Is Hard

The three case studies above all circle the same central problem, approached from different angles. It is a problem worth understanding precisely because examiners love to test it.