Cambridge IGCSE Marine Science 6: Human influences on the marine environment

Topic 6 evaluates how people depend on, damage and manage marine systems. Cambridge 0697 covers tourism, fisheries, aquaculture, energy, oil, plastics, eutrophication, climate change and conservation. Strong answers balance environmental, social and economic evidence instead of treating every use as wholly beneficial or harmful.

Value, pressure and sustainability

Marine ecosystems support recreation, tourism, timber and building materials, coastal protection, food, medicines, fisheries and nursery habitat. Human activity can also create noise, light, litter, trampling, souvenir collection, boat and diving damage, land reclamation, infrastructure, dredging, mangrove logging, blast fishing, shrimp-farm conversion and oil spills.

Declining populations may become endangered and face extinction. A sustainable resource or activity can continue at its current rate without exhausting the resource or causing unacceptable environmental damage. This definition requires both continuity and ecosystem condition.

Tourism and ecotourism

Tourism brings employment, income and infrastructure. Ecotourism focuses on natural areas while encouraging environmental and cultural understanding, appreciation and conservation. It can fund Marine Protected Areas and conservation groups, but the label alone does not guarantee low impact.

Costs include competition for land or water, pollution, ecosystem damage, organism collection and behavioural effects from wildlife interaction. A named case such as the Galapagos Islands or Great Barrier Reef should connect visitor activity to a particular ecosystem response.

Education, legislation and strategic planning can reduce impacts. Renewable energy, restricted water use, single-use-plastic bans and limited motorised transport offer benefits but also costs, enforcement needs and possible effects on local livelihoods. Evaluation needs a criterion, such as ecological recovery, fairness or long-term income.

Fisheries

Marine harvesting supplies food, employment and income. Netting and trapping include cast nets, pelagic and beam trawls, purse seines, gill or drift nets and basket traps. Angling includes trolling, longlining and pole-and-line fishing. Impacts depend on selectivity, seabed contact, bycatch, lost gear and scale.

Charts, compass roses, GPS, sonar and radar support navigation and locating fishing grounds or hazards. Population growth and demand can drive harvest beyond replacement. Management includes limits on boat or net size and mesh, quotas and licences, closed seasons, MPAs and international agreements. Sustainable harvest maintains stocks for future generations without disrupting food chains.

Fish aggregating devices attract fish to a known location and can reduce search time, but they may concentrate juvenile or non-target species and increase overharvest. Their value depends on design, monitoring and fishing method.

Aquaculture

Aquaculture produces macroalgae, salmon, grouper, shrimp, mussels, oysters and sea cucumbers. It can supply food and reduce pressure on wild stocks, yet waste, disease, escapes, habitat conversion and feed demand can damage ecosystems.