3.2 Human impact on biodiversity

Direct threats remove organisms; indirect threats change the conditions they need to survive.

Overharvesting, poaching and capture for the illegal pet trade remove organisms directly. Habitat loss, pollution, climate change and invasive alien species alter space, resources or interactions indirectly. Both groups can be human-driven.

Poaching kills elephants directly; road building fragments the habitat and indirectly lowers breeding success.

Direct if it kills them; indirect if it first changes habitat or food conditions. State the first effect.

‘Human-caused’ is not the direct/indirect distinction; classify the immediate mechanism.

Multiple pressures can amplify damage when the first one removes the ecosystem’s ability to respond to the second.

Trace pressure → lost function or diversity → weaker resilience → larger later impact. This is more than listing two threats side by side.

Overfishing simplifies a reef food web; later heat stress causes more severe bleaching because fewer functional groups support recovery.

The second impact is larger after the first pressure than it would have been in the intact system.

Two pressures are not automatically synergistic; show the mechanism that changes resilience.

Alien means outside its native range; invasive means the introduced population spreads and causes harm.

Follow arrival → release from controls → increase → impact mechanism → targeted management. Non-native status alone does not prove harm.

Introduced grey squirrels expand, compete with red squirrels and carry squirrelpox; control and habitat refuges target those pathways.

Harmful spread and a demonstrated ecological mechanism are also required.

Do not manage every non-native species identically; identify actual spread, harm and feasible intervention.

The International Union for Conservation of Nature (IUCN) publishes the Red List, which combines population trend, abundance, geographic range, breeding potential and known threats to judge global extinction risk.

Categories run from Least Concern (LC) through increasing levels of threat to Extinct in the Wild (EW) and Extinct (EX). Small or declining populations, narrow or fragmented ranges and low breeding potential raise vulnerability; Data Deficient means evidence is insufficient, not that risk is low.

A widespread species with stable numbers may be lower risk than a rapidly declining species with a small range, even if the latter is locally common.

Uncertainty about risk; prioritize better evidence rather than assuming safety.

A Red List category is a global risk assessment, not a direct prescription for one local action.

A status turns evidence of vulnerability into a shared priority signal, but the best action depends on threat, rights and feasibility.

Governments may fund protection or trade controls; NGOs may restore habitat or monitor; citizens may change consumption or report observations. Match the actor’s lever to the dominant pressure.

If habitat conversion is the main threat, a trade campaign alone is weaker than land-use protection plus local enforcement.

Actors have different powers, constraints, local rights and responsibilities.

Status guides priority; it does not dictate one universal intervention.

A conservation case is complete only when it links the cause of decline, ecological or social impact, intervention and evidence of the outcome. Compare different status pathways rather than treating every threatened species as the same problem.

For each case, keep action separate from success: a law is an intervention, while a measured population or status change is outcome evidence. Also trace consequences through food webs, ecosystem services, livelihoods or culture where the local evidence supports them.

Use the same chain for all three cases: pressure → decline → ecological or social consequence → conservation response → measured outcome.

Conservation effort is not automatically conservation success; status and population evidence must show whether risk actually changed.

A commons fails when each user captures a private short-term benefit while costs spread across the shared resource and community.

Trace private gain → shared cost → resource feedback → governance response. Rules work only if they cover enough users, are monitored and change incentives.

In a fishery, each fisher gains by catching fish before others, but combined harvest can push the stock below recovery. In an ocean gyre, each user gains convenience from disposable plastic while cleanup and ecological damage are spread across the shared ocean.

Users can gain by defecting while others restrain themselves; enforcement or cooperation must alter that payoff.

A commons is not ‘any public place’; the key is shared access plus an incentive that depletes it.

A hotspot combines irreplaceable endemic diversity with severe habitat threat, so protection can deliver global benefits while creating local development trade-offs.

Clearing a small area can remove species found nowhere else. Agriculture, logging, mining and roads also provide jobs or revenue, so conservation must address who bears opportunity costs.

Protecting a forest patch may save an endemic primate while restricting a road project; compensation or alternative livelihoods affect feasibility.

It protects high-irreplaceability habitat and states how local livelihoods and costs are handled.

Global biodiversity value does not erase local rights or automatically make one land use just.

A Key Biodiversity Area (KBA) is a site that contributes significantly to the global persistence of biodiversity because it supports threatened or geographically restricted biodiversity, ecological integrity, important biological processes or irreplaceable features.

A strong justification names the biodiversity feature, explains why losing it has global rather than only local consequences, and identifies the pressure that conservation must address.

The Amazon case emphasizes endemic terrestrial diversity and climate–water regulation; the Coral Triangle emphasizes irreplaceable marine diversity and reef-dependent livelihoods.

High species count alone is not enough: connect the named site to threatened, restricted, ecologically important or irreplaceable biodiversity and to its global persistence.

Palm-oil decisions must weigh income and jobs against forest conversion, fragmentation, carbon release and threatened-species loss.

A credible compromise prevents conversion of high-conservation-value habitat, traces supply chains, includes smallholders and monitors outcomes—not merely a label.

Higher yield on existing farmland may meet demand with less new clearing than expanding into intact forest, if enforcement is real.

Actual land-use change, habitat condition, worker/smallholder outcomes and verified supply-chain compliance.

‘Certified’ does not prove zero impact; inspect the standard, monitoring and leakage of expansion elsewhere.

Cultural burning can create a patchwork of vegetation ages and reduce fuel continuity when guided by place-specific knowledge, authority and timing.

Assess ecological outcome and governance together. Dispossession, land conversion, legal barriers and changed fire weather can disrupt practice; communities are diverse and adapt.

Low-intensity burns at different times can maintain food resources and reduce connected fuel, unlike one severe uncontrolled fire.

Outcome depends on intensity, season, patchiness, species and authority—not fire alone.

Do not stereotype one Aboriginal practice as universal or treat external disruption as an internal cultural defect.

Environmental justice asks who gets benefits, who bears costs, who decides and whose rights or knowledge count.

A protected area can conserve habitat while imposing livelihood or cultural losses on displaced communities. Fairer approaches secure rights, informed participation, remedies and benefit-sharing or co-management.

The Maasai around the Serengeti illustrate the justice issue: conservation relocation or access restrictions can protect habitat while removing people from land that supported food, livelihoods and culture. The audit must examine rights, consent, decision power, remedies and benefit-sharing.

Participation is meaningful only when affected communities can influence decisions and their rights, losses and remedies are addressed before implementation.

A broad conservation benefit does not cancel unequal local costs or make displacement automatically fair.

Biosphere integrity links diversity and ecological functions; losing species or populations can weaken regulation of water, nutrients, carbon and energy.

Trace biodiversity loss → reduced functional redundancy → weaker process → feedback. Boundary assessments indicate risk and uncertainty; they do not give one exact global tipping date.

Forest degradation lowers carbon uptake, which can increase warming and further stress the forest—a feedback chain, not proof of a fixed endpoint.

It connects measured loss to ecosystem function and Earth-system consequences, with scale and uncertainty stated.

High risk is not certainty of collapse; distinguish evidence of pressure from prediction of timing.