Explain the interrelationship between people and ecosystems, analyse the causes and consequences of ecosystem and biodiversity change, and evaluate strategies for managing ecosystems sustainably.

What this dot point is asking

You need to show that people and ecosystems are interdependent, not separate. Strong answers identify specific causes of ecosystem change, trace consequences through environmental, social and economic systems, and judge how well management strategies restore sustainability.

The interrelationship between people and ecosystems

An ecosystem is the web of interactions between organisms (plants, animals, microbes) and the abiotic environment (soil, water, climate). People sit inside ecosystems and rely on ecosystem services. These are usually grouped as provisioning services (food, timber, fresh water), regulating services (climate regulation, pollination, water purification), supporting services (soil formation, nutrient cycling) and cultural services (recreation, spiritual and Indigenous connection to Country).

Because people depend on these services, changes to ecosystems flow back into human wellbeing. Clearing a wetland removes its water-filtering and flood-buffering function, which then raises costs and risk for nearby communities. This two-way relationship is the heart of the dot point.

Causes of ecosystem and biodiversity change

The major direct drivers of ecosystem change are habitat loss, overexploitation, pollution, invasive species and climate change. Australia provides clear cases:

• Land clearing for agriculture has removed roughly 40 percent of Australia's forest cover since European settlement, fragmenting habitat for species such as the koala, now listed as endangered in Queensland, New South Wales and the ACT (2022).
• Invasive species are a leading cause of extinction. Feral cats kill billions of native animals each year, and the cane toad, introduced in 1935 to control beetles in Queensland sugar cane, has spread across northern Australia, poisoning predators such as quolls.
• The Great Barrier Reef has suffered repeated mass coral bleaching events (2016, 2017, 2020, 2022 and 2024) driven by marine heatwaves, showing how climate change degrades a globally significant ecosystem.

Consequences across the three systems

SACE rewards answers that follow consequences through environmental, social and economic systems. Loss of biodiversity reduces ecosystem resilience, so systems recover more slowly from disturbance such as drought or fire. The 2019-2020 Black Summer bushfires burned over 18 million hectares and are estimated to have killed or displaced around 3 billion animals, pushing some species closer to extinction and damaging tourism economies.

Socially, degraded ecosystems threaten food and water security and weaken the cultural connection of Aboriginal and Torres Strait Islander peoples to Country. Economically, the Great Barrier Reef supports tens of thousands of jobs and contributes billions of dollars annually to the Australian economy through tourism, so reef decline carries a direct financial cost.

Strategies for sustainable management

Management operates at several scales. International agreements such as the Convention on Biological Diversity and the 2022 Kunming-Montreal Global Biodiversity Framework set targets to protect 30 percent of land and sea by 2030. Nationally, Australia uses protected areas, including the National Reserve System and Indigenous Protected Areas, which now make up a large share of Australia's conservation estate and combine traditional knowledge with formal management.

Local strategies include revegetation, feral-animal control, cultural burning led by Traditional Owners, and reef interventions such as coral nurseries and crown-of-thorns starfish removal. The best answers evaluate these. Protected areas conserve habitat but can fail without funding and enforcement; cultural burning reduces fuel loads and supports biodiversity but needs scale and Indigenous leadership to work.

Linking it together

A complete response treats people and ecosystems as one interdependent system, uses specific Australian and global cases such as the Great Barrier Reef and feral species, follows consequences through environmental, social and economic systems, and reaches a judgement about which management strategies best restore sustainability. That structure mirrors the geographical skills and applications criteria the SACE Board assesses.