What Is Biodiversity: Definition, Importance, Major Threats and Ecosystem Roles

Last updated: January 2026

Nature’s balance depends on the diversity of life — biodiversity.

More and more, we understand Earth as an interconnected system where species and natural processes rely on one another. Yet much of this living web has been damaged in the name of growth and progress, and biodiversity continues to decline even when the risks are well known.

Scientists warn that ongoing habitat destruction and species loss threaten the stability we depend on — food, clean water, pollination, and climate regulation. The good news is that decline isn’t inevitable. But reversing it starts with understanding what biodiversity is, why it matters, and what puts it at risk.

In this guide, you will learn what biodiversity is, why it matters, what threatens it, and how it can be protected.

The definition: what is biodiversity?

Biodiversity (also biological diversity or biotic diversity) is the variety of life on Earth, across genes, species, and ecosystems.

The term “biodiversity” refers to every living thing: plants, animals, bacteria and even humans. Biodiversity is often spoken of as having three different levels that can be examined:

• species diversity
• genetic diversity
• ecosystem diversity

These levels shape species richness, resilience, and overall ecosystem function.

What is species diversity?

When people think about biodiversity, they often think of animals — birds, fish, mammals, reptiles, amphibians, and insects. But species diversity also includes plants, from large trees and flowering plants to grasses, mosses, and lichens, collectively known as flora and fauna.

It also includes organisms that are rarely noticed: soil-dwelling animals and microorganisms that break down organic matter and maintain fertile soil. These countless species form the foundation of ecosystem function.

What is genetic diversity of species?

Biodiversity also exists within species as genetic diversity (genetic variation). Genetic diversity looks to the variety of genes within a species. This is important because a greater variety of genes within a population helps species to better adapt to a habitat.

For example, if an area has been deforested and the remaining animal community is small, the animals do not have much choice in mating. In a larger population, one monkey, for example, might mate with another monkey outside its family that has genes that protect it from a novel virus or parasite.

In small, isolated populations, limited genetic variation can make species more vulnerable. When individuals share similar genes, a single disease or environmental stress can affect the entire population at once. They just do not have a capability to adapt in time. Small, isolated populations with low genetic diversity are more likely to be wiped out by a single disease outbreak.

What does the ecosystem diversity mean?

Some scientists take a step back instead of closer when considering biodiversity.

That is the third level called ecosystem diversity – the range of ecosystems and habitat types in a region. An ecosystem is a biological community living within a certain geographical area. It can be, for example, all of the life within a jungle, a marine ecosystem, a desert or a grassland.

And one geographical area may have several ecosystems. For example, the area of Tropical Andes is rich in ecosystem diversity as it includes mountains, cloud forests, grasslands, woodlands and even tropical rainforests.

Some regions stand out globally because of their exceptionally high ecosystem and species diversity. This is why regions like these are often discussed as biodiversity hotspots.

Why is biodiversity important?

Our existence depends on Earth having an abundance of biological diversity.

Biodiversity supports the health of all living species. Without it, we could not obtain food, clean air, or fresh water. The oceans, too, must sustain a wide variety of life if we hope to rely on seafood for nourishment.

All the natural processes that provide fresh air, rainfall, water cycles, and fertile soil — as well as materials for shelter and clothing — depend on biodiversity.

Biodiversity and ecosystem functioning

It may be easiest to understand how interconnected life is by looking at a single ecosystem. Fruit trees grow in fertile soil. That soil is formed from fallen branches and leaves that decompose, a process made possible by microorganisms.

Insects, worms, and grubs feed on these microorganisms. In turn, they become food for rodents, small mammals, birds, reptiles, and larger animals. Pollinators such as bees and butterflies depend on specific flowering plants, and they play a crucial role in pollination — without which fruit could not grow. Birds and small mammals later help disperse seeds, allowing future trees to develop.

This interdependence is one example of the ecosystem services biodiversity provides.

Biodiversity and climate regulation

Ecosystems do more than provide food and shelter — they also regulate the climate.

Healthy forests and grasslands absorb carbon dioxide, a major greenhouse gas, while producing oxygen. This helps moderate Earth’s temperature and makes life possible. However, fossil fuel use and deforestation are disrupting this balance. As forests are removed, more carbon dioxide remains in the atmosphere, intensifying global warming and further damaging ecosystems that could otherwise help absorb it.

This cycle reinforces itself: rising temperatures dry out ecosystems, increase wildfire risk, and reduce the planet’s ability to regulate climate.

Biodiversity in oceans

Biodiversity in the oceans is equally critical. For a long time, oceans have acted as major carbon sinks and a source of oxygen. Phytoplankton, microscopic, plant-like organisms, form the base of the marine food web and absorb large amounts of carbon dioxide.

Scientists estimate that phytoplankton produce between 50 and 85 percent of Earth’s oxygen. However, warming oceans have already led to significant phytoplankton loss, threatening marine food chains and global oxygen production.

Biodiversity and water cycles

Biodiversity also plays a critical role in the water cycle. Moisture evaporates from forests, grasslands, and oceans, later returning to Earth as rain or snow. When these ecosystems are damaged or lost, their contribution to rainfall diminishes.

Warming temperatures accelerate evaporation from oceans while drying out land ecosystems, increasing wildfire risk and reducing long-term water availability. Earlier snowmelt and prolonged dry periods are already affecting many regions. We are seeing more and more habitat loss.

Biodiversity stabilizes local climates

The loss of biodiversity is increasingly linked to extreme weather events.

Ocean currents, which act like a global conveyor belt transporting heat and nutrients, depend on stable temperature differences. As oceans warm, these currents are slowing. Changes in major systems such as the Gulf Stream could alter regional climates, leading to cooler temperatures in some areas and more extreme weather patterns elsewhere.

Such shifts create conditions that many species cannot adapt to quickly enough.

Food security and crop diversity

Biodiversity is essential for food security. As climate conditions shift, many of the crops we rely on are becoming more vulnerable to pests, disease, and extreme weather.

Modern agriculture relies heavily on a small number of crop species, reducing genetic diversity. When biodiversity declines, food systems become more fragile, increasing the risk of shortages in a world with a growing population.

Livelihoods and tourism

Biodiversity also supports millions of livelihoods. Fisheries and aquaculture sustain a significant share of the global population, while tourism depends on healthy ecosystems such as coral reefs, rainforests, and wetlands.

Protecting biodiversity is not only an environmental issue. It is essential for economic stability and the well-being of communities around the world.

What are the major threats to biodiversity?

The biggest threat to biodiversity is habitat loss and land degradation, caused in most cases directly or indirectly by human activity. Habitat loss is often accompanied by habitat fragmentation, where large, continuous ecosystems are broken into smaller, isolated patches that cannot support healthy populations of species.

Large areas of land have been destroyed by mining and converted into industrial waste sites. Forests have been cleared for timber and agricultural expansion, while natural habitats have been removed to make room for urban sprawl, energy infrastructure, and manufacturing operations.

Well over 75 percent of Earth’s land is now substantially degraded. This has severe consequences for soil organisms, plants, and all species that depend on them.

Good arable land has degraded into desert in many parts of the world due to unsustainable agricultural practices such as overgrazing, over-tilling, and the use of toxic herbicides.

Pollution causes biodiversity loss

Much of our water is polluted. Over 80 percent of India’s water is severely polluted [8]. Over 40 percent of lakes and rivers in the United States are too polluted to fish or swim in [9]. The biggest source of water pollution is from industrial and agricultural waste and inadequately treated human waste.

Each day two million tons of sewage and other effluents drain into the world’s waters, carrying debris.

The Great Pacific Garbage Patch is one of five offshore plastic accumulation zones in the world’s oceans and it alone covers an approximate surface area of 1.6 million square kilometers, an area three times the size of France.

Noise pollution too is threatening biodiversity. We are a noisy race with our machines and vehicles. The truth is that we simply don’t know the health impact on most species of our incessant noise. Many birds, fish and mammals fish rely upon sound waves to communicate, to sense predators, to determine direction and to find mates.

To this day, we do not know the extent of physiological injury that may be caused to underwater life by the sound of boat motors.

Far-reaching effects of deforestation on biodiversity

Deforestation for timbering and agricultural expansion is the single biggest contributor to biodiversity loss and it shows no signs of stopping.

When an area is deforested, the animals who lived there or roamed through the area lose their habitats and feeding or mating grounds. If they are not killed outright which happens to all of the plant species and to animals, amphibians, reptiles and birds that cannot escape in time, then they must quickly find a place to relocate and adapt if possible.

Each particular instance of deforestation presents its own horrifying scenario. For example, the ongoing deforestation in Indonesia has orphaned countless young orangutans who need their mother’s nurturing for at least seven years to teach them survival skills. Many of these young have provided additional income for those destroying the forests who capture them until they can sell them through the exotic animal trade network where they are destined to live miserable lives under brutal conditions.

Orangutans share 97 percent of our DNA. They are intelligent and have feelings we can readily identify with.

Deforestation takes place all around the world, not just in the more highly publicized remote areas. It is taking place all around us and each time a swath of forest is felled, we lose biodiversity and make the neighboring remaining habitats more vulnerable to pests, diseases and ultimate extinction.

Invasive species reduce local biodiversity

Our global interconnectedness is promoting the spread of invasive species which then dominate and unbalance an ecosystem. Many of the problems we are experiencing from the spread of invasive species are the result of deliberate introduction of plant or exotic animal species to another environment through uneducated curiosity.

Other species have simply hijacked on carrier vessels, like the microbes that attach themselves to ship hulls and then devastate destination’s coastal marine ecosystems. Some even travel across species boundaries, possibly via consumption, to a new species that has no resistance and then spread across the globe… like the Corona Virus has, traveling within human bodies.

Overfishing and hunting

Fishing and hunting also threaten biodiversity.

Overfishing occurs when fish are caught faster than populations can replenish. More than one-third of global fisheries are overexploited, and destructive practices such as trawling and bycatch kill vast numbers of non-target species.

On land, hunting and the illegal wildlife trade have contributed significantly to species decline. Both legal and illegal hunting have driven many species toward extinction and continue to threaten wildlife populations worldwide.

We have driven nearly 52 percent of our wildlife species to extinction since 1980. In addition to deforestation, pollution and habitat loss, the illegal wildlife trade and hunting have played major roles.

Legal hunters kill tens of millions of animals per year and poachers hunting illegally have eliminated just as many [12]. Whether done legally or illegally, all types of hunting have led to extinction of species. If not controlled, many more animals will be doomed to extinction.

Climate change eradicates species

Climate change is accelerating biodiversity loss by altering temperature, rainfall patterns, and ocean chemistry faster than many species can adapt.

Melting glaciers threaten Arctic species, warming oceans disrupt marine ecosystems, and shifting climates interfere with migration and breeding cycles. Species that evolved under stable, pre-industrial climate conditions are increasingly unable to survive rapid environmental change.

Biodiversity loss: what are the consequences?

The loss of biodiversity has far-reaching consequences for ecosystems and human societies alike. When species disappear or populations decline, the balance within ecosystems begins to unravel.

Ecosystems depend on a wide variety of organisms to function properly. As biodiversity declines, ecosystems become less stable and less resilient to disturbances such as disease, extreme weather, and climate change. This makes recovery slower and, in some cases, impossible.

Ecosystem collapse and species extinction

One of the most direct consequences of biodiversity loss is species extinction. When key species disappear, this can trigger food web disruption, sometimes leading to trophic cascades, where changes at one level of the ecosystem ripple through many others.

As ecosystems lose complexity, they become more vulnerable to further degradation. Once a certain threshold is crossed, ecosystems may collapse entirely, resulting in the permanent loss of habitat and species.

Yes, species have always been going extinct and new ones evolving. The concern is the recent dramatic increase in the rate of extinctions. Even a greater threat to biodiversity than the loss of individual species is the wholesale loss of ecosystems that sustain them.

Threats to food, water, and human health

Biodiversity loss also threatens essential resources. Declining biodiversity reduces food security by weakening agricultural systems and fisheries, making them more susceptible to pests, disease, and environmental stress.

Water systems are affected as well. Degraded ecosystems are less effective at filtering water, regulating floods, and maintaining stable water cycles. As a result, clean and reliable water supplies become harder to secure.

Human health is also at risk. Many medicines originate from plants, animals, and microorganisms. As species disappear, so does the potential for future medical discoveries.

Economic and social consequences

The impacts of biodiversity loss extend beyond the natural world. Millions of people depend on healthy ecosystems for their livelihoods, particularly in fisheries, agriculture, and tourism.

As ecosystems degrade, economic instability increases, disproportionately affecting communities that rely most directly on natural resources. In the long term, biodiversity loss can contribute to poverty, displacement, and social conflict.

Why biodiversity loss is difficult to reverse?

Unlike some environmental problems, biodiversity loss is often irreversible. Species extinction is permanent, and ecosystem recovery can take decades or centuries, even under favorable conditions.

Because biodiversity loss accelerates other environmental challenges — including climate change and land degradation — its consequences compound over time.

How can we protect biodiversity?

The solutions are within our reach and there are many opportunities for hands-on efforts. Conservation efforts focus on expanding protected areas, reducing human pressure on ecosystems, and supporting ecosystem restoration to help degraded habitats recover. Good news is that we understand enough to take dramatic effective measures to protect biodiversity. We have the technology and the understanding.

Here are just a few suggestions how we can protect biodiversity:

Protecting oceans and stopping overfishing

We must stop overfishing and destruction of ocean habitats and marine populations by passing and enforcing regulations.

Presently only one percent of the oceans are protected from fishing [14]. The renowned naturalist David Attenborough predicts that we could save the coral reefs and mangroves with the life they sustain as important nurseries if we only protected one-third of our coastlines. Watch the video for more information.

We can designate times and routes for seafaring vessels that respect the migratory patterns of aquatic life.

Tackling the problem of overhunting and poaching

We have to stop overhunting and poaching by passing and enforcing regulations. One of the most effective ways to enforce regulations is to recruiting natives to the area where wildlife is being poached. They have the best knowledge.

Building sustainable economies around biodiversity hotspots which rely upon the integrity of the surrounding nature is an excellent way to protect them. Educating people to understand the significance of their environment is a critical step to effectuating the paradigm shift that will save us as a species and the wonderful diversity of life around us.

Even small steps such as understanding why it is important to stay on the paths in local and national parks instead of insisting on taking a selfie on a slippery hill of shale and destroying critical but tenuous wildflowers underfoot, can go a long way to preserving biodiversity.

Sustainable food production

We can change our agricultural and food consumption practices to waste less and to grow a variety of healthy food employing preindustrial methods that enrich the soil rather than destroying its life and inundating land, air, the food product itself and ultimately water with toxic chemicals.

On an individual level we can support local farmers’ markets to help small family farmers. Plant native grasses, flowers and shrubs to attract pollinators and build soil and habitats in backyards and urban green spaces.

Changing our daily lifestyle

We need to reduce greenhouse gas emissions by switching to green technology for our heating, electricity and transportation needs. We have to regulate the manufacture and use of plastic, single-use and non-biodegradable items. On an individual level, we should consume less.

The fashion industry has garnered negative attention in recent years over its water pollution and usage with the revelation that making a single t-shirt uses 2720 (!) liters of water [15]. Yet this does not appear to have altered mainstream buying patterns. If people were more mindful of the far-reaching consequences of their actions, would they change them?

Education is a first step. Making sure this is in a school’s curriculum would be civic-minded. Meanwhile, look to the origin of products when buying. The Forest Stewardship Council or Rainforest Alliance both certify products that do not contribute to habitat destruction and protect the human rights of indigenous people where they are grown.

The Marine Stewardship Council certifies seafood from sources committed to sustainable fishing.

Consider the cradle-to-grave impact of each product you buy. Current landfill technology is subpar and does not ultimately ensure the sanctity of our groundwater [16]. Too much waste still ends up in waterways and it could be the plastic bag or wrapping that you used that blew off the collection truck, which not only pollutes the water but also choked a fish or bird.

We can also turn to recyclable materials for building shelter rather than always relying upon timber.