Population Matters



Ecosystems are complex webs of interdependency between species. They provide humanity with many benefits, including environmental regulation, recycling, pollination, and as sources for new medicines and materials. Their resilience depends partly on their variety, which is threatened by human development and resource exploitation.


Over half of vertebrate species - like this golden toad - have been lost since 1970
Over half of all vertebrate species have been lost since 1970

Ecosystems, interdependent webs of living organisms and natural resources, are essential to sustain all life on earth. Throughout earth’s history, healthy ecosystems have usually been resilient enough to adapt to gradual environmental change. Existing species may evolve or new species move in, in response to small changes in the habitat without collapse of the entire system.

Biodiversity, the range and variation of species in an ecosystem, is a major factor in its resilience. If the environment changes and some organisms can no longer thrive, others will take their place. Many of the species vital to healthy ecosystems may appear insignificant. Insects, for example, play an essential role in pollinating food crops.


The sheer variety of species and habitats on the planet is vast. This is of vital importance because it underpins the functioning of the ecosystems on which we depend for water and food, health and recreation.

Pollinating insects are declining due to human impact
Pollinating insects save UK farmers £440m per year, but are declining due to human impact

The importance of biodiversity is often undervalued even though it helps humanity by:

  • regulating the chemistry of the atmosphere and water supply;
  • providing crucial ecological services such as the mass pollination of food crops throughout the world;
  • recycling nutrients crucial to the maintenance of the earth’s soil fertility; and
  • supplying genetic variants for crop development and the creation of new medicines.

Where elements of biodiversity are lost, ecosystems become less resilient to sudden pressures such as disease and climatic extremes.

Biodiversity is falling in extent and variety through human development. This includes habitat loss, resource exploitation, urbanisation, intensive agriculture, pollution and invasive species. Climate change has the potential to make the impact of all of these issues worse and to make its own direct impact on biodiversity.

The sixth mass extinction

Since life appeared on earth, there have been several mass extinctions in which many of the earth’s species were wiped out because of climate change, volcanic activity, the impact of an asteroid or reasons we have not yet discovered. The plants and animals which currently live on Earth have continued to evolve over the 65 million years since the last mass extinction. But many scientists consider the huge reduction in biodiversity since the emergence of humans is now on the scale of another mass extinction. This is known as the Holocene or Anthropocene extinction.


Habitat loss

Ever more people need ever more space. Human activity continues to encroach on natural environments, thereby destroying the habitats of countless species. While some progress has been made in slowing the rate of loss of tropical forests and mangroves, serious declines are also being seen worldwide in freshwater wetlands, sea ice habitats, salt marshes, coral reefs, seagrass beds and shellfish reefs.


Ever more people need ever more stuff. Humankind’s relentless consumption of resources such as timber, oil and minerals is continuing to destroy natural habitats around the globe. We are also putting enormous pressure on populations of wild species, both by hunting in the developing world and by large-scale industrial fishing in our seas.


Ever more people need ever more homes. In most industrialised countries and a growing number of developing ones over half the population live in cities. Properly designed cities and agricultural systems can sometimes support people with a lower impact on biodiversity than can a more evenly spread population. But as our numbers rise, cities and industrial areas are growing and merging into each other, fragmenting the remaining habitat leaving isolated “islands” of natural populations of plants and animals too small to survive.


Intensive agriculture

Ever more people need ever more food. In order to meet the unsustainable consumption patterns of the developed world and feed the numbers of people living on the Earth today, humanity has developed agricultural systems which rely on monocultures, artificial fertilisers and pesticides. Monocultures are increasingly susceptible to disease, pesticide use destroys insect populations indiscriminately, whilst fertiliser runoff pollutes water courses. In addition, the growing pressure on food supplies means an increasing proportion of agricultural land is farmed intensively, with fewer off seasons or fallow years in which to recover.


Ever more people produce ever more waste and pollution. As well as affecting the lives of humans, noise, light and chemical pollution can disrupt wildlife behaviour. Light from human activities makes it harder for predator species to catch their prey. Noise pollution interrupts both hunting and mating signals in many species, disturbing natural behaviour.

The build-up of phosphates and nitrates from agricultural fertilisers and sewage effluent is creating long-term algal blooms in freshwater lakes and inland water systems, causing fish stocks to decline, with serious implications for food security in many developing countries.


As populations increase, the disposal of waste becomes an increasingly serious issue. Pollution will always be a consequence, whether we use land fill, incinerators or disposal at sea and in watercourses. The disposal of toxic materials poses significant additional hazards and problems.

Invasive species

As a consequence of the introduction of non-native species to some areas, such as rabbits in Australia or goats on St. Helena, we have put many vulnerable ecosystems at risk, threatening native ecologies and diminishing biodiversity.

Read more about ecosystems and biodiversity.

Next: Society

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