Reasons for the decline of animals and plants in some countries

Across many countries, populations of wild animals and native plants are shrinking. Some argue the primary drivers are human activities such as habitat destruction and overexploitation, while others point to natural forces, including climate variability and disease. In my view, both contribute, but human pressures are the dominant cause in most contexts.

Those who emphasise human responsibility highlight several direct mechanisms. Habitat loss from deforestation, road building and urban sprawl fragments ecosystems and leaves species with too little space to feed or reproduce. Overexploitation—poaching and overfishing—pushes targeted species toward collapse, while pollution from pesticides, plastics and untreated effluent poisons food chains. For instance, large-scale clearing in Borneo has cut orangutan ranges and nesting sites, and agricultural runoff in the Gulf of Mexico regularly triggers dead zones that kill fish and invertebrates.

Others stress that nature itself can cause sharp declines. Prolonged droughts, natural wildfires and temperature anomalies can decimate vegetation and the animals that depend on it. Pathogens also play a role: the chytrid fungus has devastated amphibian populations on several continents. Ocean heatwaves associated with El Niño events have bleached and killed corals without any local human interference. In island ecosystems, storms and naturally introduced competitors can quickly unbalance small, isolated populations.

Nonetheless, in most countries the scale and speed of decline are best explained by human land use and emissions. The relative weight of causes varies by biome and governance: arid nations may see drought magnify pre-existing stress, while islands are acutely vulnerable to invasive species; countries with weak enforcement suffer more from poaching and illegal logging. Therefore, policy should primarily curb human pressures—protect habitats, regulate harvests and reduce pollution—while also investing in resilience to natural shocks, such as drought-ready water management and disease monitoring.

In short, declines in animals and plants stem from both human and natural factors. Natural events can trigger sudden losses, but pervasive human activities generally drive the long-term downward trend. A balanced response acknowledges this reality: prioritise reducing human impacts, and prepare ecosystems to withstand the natural disturbances that will continue to occur.