Main Causes of Biodiversity Loss: Why Species and Ecosystems Are Disappearing

Last updated: January 2026

Biodiversity did not begin declining by accident. For most of Earth’s history, species and ecosystems have adapted to gradual environmental change. Today, however, the pace and scale of human activity are altering natural systems faster than they can respond.

As land is cleared, resources extracted, water diverted, and ecosystems reshaped to meet growing demand, the conditions that support biodiversity are steadily eroded. These pressures rarely act in isolation. Instead, multiple human activities overlap and reinforce one another, accelerating biodiversity loss across land and sea.

Biodiversity underpins the stability of ecosystems and the processes that sustain life on Earth.

Understanding the causes of biodiversity loss means examining the specific ways modern societies transform natural environments and how these changes disrupt the ecological processes that sustain life.

Major causes of biodiversity loss

Areas rich in biodiversity are healthier, more resistant to disease, and better able to recover from environmental stress. When this diversity is reduced, ecosystems become simpler, weaker, and more vulnerable to disruption.

The loss of biodiversity is not driven by a single factor. It results from multiple human activities that alter land, water, and climate systems, often acting together and reinforcing one another. 

#1 Urban sprawl

Urban sprawl is one of the leading drivers of biodiversity loss. As populations expand, land is cleared to build homes, businesses, and infrastructure at an unprecedented rate.

When land is converted for urban use, habitats of native flora and fauna are destroyed. Entire ecosystems may be eliminated, while surviving populations become isolated from one another. This process leads to habitat loss and habitat fragmentation, where once-continuous ecosystems are broken into smaller, disconnected patches.

Buildings, parking lots, highways, and pipelines divide animal and plant habitats. Large, connected populations are generally more stable than small, isolated ones because they maintain greater genetic diversity and long-established ecological relationships. When habitats are fragmented, these relationships are disrupted.

As populations become smaller and more isolated, they are increasingly exposed to pressures such as pests, disease, predators, and changing environmental conditions. This makes it more difficult for species to maintain viable populations over time.

Urban expansion has also resulted in the removal of ecosystems with specialized functions, such as mangrove swamps and coral reefs. These ecosystems support high levels of biodiversity and play a distinct role in shaping local environmental conditions.

Urban sprawl alters landscapes permanently. Cities are typically designed around economic and practical requirements, with limited consideration for preserving local biodiversity. As a result, urbanization continues to reshape ecosystems and contributes significantly to ongoing biodiversity loss.

#2 Unsustainable agricultural practices

Modern industrial agriculture is closely linked to biodiversity loss. What began as an effort to increase food production and reduce crop losses has developed into a system that relies heavily on chemical inputs, mechanization, and intensive land use. Over time, this approach has reshaped landscapes and altered the biological foundations of many ecosystems.

Industrial agriculture is dominated by practices that disrupt soil structure, water systems, and native habitats. These include clearing large areas of land, compacting soil with heavy machinery, emissions from diesel-powered equipment, and intensive tilling that breaks down soil structure and the fungal networks essential for soil health. The widespread adoption of monoculture farming, where a single crop variety is grown over large areas, further reduces genetic diversity and simplifies local ecosystems.

Chemical inputs play a central role in industrial farming systems. Synthetic fertilizers, herbicides, pesticides, and fungicides are applied regularly to suppress competing plants, insects, and diseases. While these inputs support short-term yields, they alter soil chemistry, contaminate surrounding water bodies, and reduce populations of non-target organisms such as birds, insects, and pollinators.

As biological activity in the soil declines, farmland becomes increasingly dependent on external inputs to remain productive. Degraded soils lose their capacity to support diverse life forms, and agricultural systems become less resilient to stress. In response, farming operations often expand into new areas, converting forests, wetlands, and grasslands into cropland or pasture.

This pattern is evident in regions such as the Amazon rainforest, where forests are cleared for cattle grazing, and in parts of Southeast Asia, where oil palm plantations have replaced diverse tropical forests. These land-use changes result in the removal of complex ecosystems and the loss of habitat for native species.

Wild animals and insects have evolved in close association with native plant communities. When diverse ecosystems are replaced by a single crop species, only a limited range of organisms can persist. Simplified agricultural landscapes support fewer ecological interactions and lack the natural checks and balances present in more diverse systems.

Such systems are inherently unstable. When crop-specific pests or diseases emerge, they encounter few natural predators or controls, allowing outbreaks to spread rapidly. This reinforces reliance on chemical treatments and further entrenches practices that drive biodiversity loss.

For a more detailed examination of these dynamics, see our article on the disadvantages of monoculture farming.

#3 Deforestation

Deforestation is one of the most significant drivers of biodiversity loss. The large-scale removal of forests transforms landscapes, alters ecological processes, and disrupts the conditions that support diverse plant and animal life.

Forests — particularly tropical forests — play a central role in regulating environmental systems. They store large amounts of carbon in vegetation and soil, and their removal releases this carbon back into the atmosphere. As forest cover declines, this regulatory function weakens, altering local and regional environmental conditions.

In some regions, this shift is already underway. Over recent decades, extensive forest clearing in Southeast Asia for timber extraction and oil palm plantations has reduced primary forest cover to the point where remaining forests no longer offset carbon emissions. Similar pressures are now affecting other major forest systems.

The Amazon rainforest remains a net carbon sink, but continued deforestation for cattle pasture and the spread of wildfires are pushing large areas toward a critical threshold. As forest structure is degraded, the ecological processes that maintain stable forest conditions become increasingly disrupted.

At the landscape level, deforestation leads directly to habitat loss and habitat fragmentation. Logging roads, clear cuts, and forest conversion break continuous forest into smaller, isolated patches. These fragmented habitats no longer provide the stable conditions required by many species.

For plants, forest removal alters shading, humidity, temperature, and nutrient availability. For animals, it reduces shelter, food resources, and opportunities for reproduction. As habitats shrink and become disconnected, species that evolved within intact forest systems struggle to persist.

Less adaptable species are particularly affected. Even modest changes in forest structure or microclimate can exceed their tolerance limits, initiating population decline and accelerating biodiversity loss.

#4 Overexploitation of natural resources and living organisms

For much of human history, Earth’s natural resources were treated as if they were limitless. Timber extraction, mining, quarrying, drilling for oil and gas, trapping, hunting, and fishing were carried out under the assumption that natural systems could continually absorb exploitation without long-term consequences.

Over time, it has become clear that these resources are finite. The extraction and processing of raw materials release toxic byproducts into air, soil, and water. Fossil fuel use alters atmospheric chemistry and ocean conditions, while petroleum-based products such as plastics accumulate in ecosystems. At the same time, the intensive harvest of wildlife and marine species reduces population sizes and disrupts ecological balance.

As global population growth and consumption intensify, pressure on natural systems increases. When extraction and harvesting exceed natural regeneration rates, ecosystems lose their capacity to maintain stable populations and biological diversity.

I. Exotic animal and plant trade

The trade in exotic animals and plants is a significant driver of biodiversity loss. Removing wild species from their native environments disrupts population structure, reproduction, and species interactions.

Species introduced outside their natural range may become invasive when released or escaped. The Burmese python in Florida’s Everglades, for example, has dramatically reduced populations of small mammals, while invasive lionfish have spread across Atlantic and Caribbean coral reefs, preying on native species and altering reef ecosystems.

Invasive plant species introduced through trade can have similar effects. Once established, fast-growing non-native plants may outcompete native vegetation, reducing habitat quality for insects, birds, amphibians, and other organisms that depend on native plant communities.

These cases illustrate how the exotic species trade can unintentionally trigger long-lasting ecological disruption.

II. Overhunting and wildlife exploitation

Overhunting places many mammal and bird species under severe pressure. Animals are hunted for food, traditional medicine, and trophies, often targeting large or reproductively important individuals.

The removal of dominant individuals or top predators alters population dynamics and disrupts ecological relationships. When predator populations decline, prey species may increase beyond natural levels, changing vegetation structure and destabilizing ecosystems through food web disruption.

Unsustainable hunting also alters human–wildlife interactions. As hunting pressure increases, contact between people and wild animals intensifies, contributing to ecological imbalance and facilitating the movement of pathogens across species boundaries.

III. Overfishing and marine resource depletion

Overfishing is one of the most widespread forms of biological overexploitation. As global demand for seafood increases, fishing pressure on marine ecosystems intensifies.

At the same time, ocean warming, pollution, and habitat degradation reduce the ability of fish populations to recover. Destructive fishing practices and high levels of bycatch further disrupt marine food webs and reduce biodiversity.

Food loss and waste compound these pressures. A substantial portion of harvested fish is discarded or lost during processing, increasing extraction pressure on already stressed marine populations. Together, these factors contribute to the ongoing depletion of marine resources and the simplification of ocean ecosystems.

#5 Tourism

Tourism contributes to biodiversity loss through multiple, interconnected pathways. Transportation associated with travel accounts for a substantial share of greenhouse gas emissions, but travel-related emissions represent only one component of tourism’s overall ecological footprint.

Accommodation and destination infrastructure also play a significant role. Tourism increases demand for energy, water, and land, while the use of single-use disposable products and the generation of food and material waste place additional pressure on local environments. In heavily visited areas, the conversion of natural land into roads, parking areas, resorts, and entertainment facilities leads to habitat loss and ecosystem degradation.

When destinations become overcrowded during peak seasons, environmental pressures intensify. Sensitive ecosystems are exposed to repeated disturbance, reducing their ability to maintain ecological balance and support diverse species.

I. Ecotourism and unintended impacts

Ecotourism is often promoted as a low-impact alternative to conventional tourism. While it aims to reduce environmental harm, increased visitation to fragile environments can still place stress on local ecosystems.

Even well-intentioned tourism may disrupt wildlife behavior, increase resource consumption, and generate waste. Without strict limits, tourism marketed as ecotourism can contribute to habitat degradation and biodiversity loss in the same way as other forms of travel.

II. Wildlife disturbance and habitat degradation

Tourism-related activities frequently disturb wildlife. In natural areas, visitors leaving designated trails may trample vegetation and damage habitats, including those supporting rare or endemic plant species. Recreational activities can interfere with feeding, breeding, and migration patterns of animals.

In some regions, tourism overlaps with wildlife exploitation. Hunting expeditions targeting declining species place additional pressure on already vulnerable populations and further disrupt ecological relationships.

III. Marine tourism and ocean impacts

Marine tourism creates additional pressures on ocean ecosystems. Cruise ships, recreational boating, and shipping traffic emit air pollutants and greenhouse gases, contributing to changes in ocean conditions.

Ship operations may also introduce pollutants directly into marine environments. Anti-fouling hull paints release toxic substances, while wastewater discharge and fuel residues contaminate coastal and open-ocean ecosystems.

Noise pollution from ship engines and sonar equipment has become an increasing concern. Many marine animals rely on sound for communication, navigation, and feeding. Persistent underwater noise alters these processes and disrupts normal behavior patterns.

#6 Unsustainable water management

Freshwater aquifers contain a limited amount of water at any given time and depend on rainfall for natural replenishment. When water is extracted faster than it can be replaced, groundwater reserves decline, altering ecosystems that rely on stable water availability.

Many industrial activities, including power generation and metal refining, require large volumes of water. In numerous cases, wastewater generated by these processes contains toxic byproducts that cannot be fully treated with existing technologies. Once contaminated, this water cannot be safely returned to natural systems, reducing its availability for aquatic organisms, plants, and surrounding ecosystems.

Intensive agriculture is one of the largest drivers of unsustainable water use. Large-scale irrigation places significant pressure on freshwater resources and contributes to land degradation in many regions.

In parts of northern China, excessive water extraction for rice cultivation has lowered water tables and accelerated desert expansion. As water availability declines, native vegetation disappears, soils degrade, and ecosystems that once supported diverse life forms are gradually lost.

A similarly dramatic example is the Aral Sea. Once among the largest freshwater lakes in the world, it was severely reduced by irrigation projects that diverted the rivers feeding it. The loss of inflow disrupted the lake’s hydrological balance and led to the collapse of its original freshwater ecosystem.

Unsustainable water management also alters ecological relationships beyond individual watersheds. When rivers and aquifers are heavily exploited upstream, downstream ecosystems receive less water, changing habitat conditions across large geographic areas.

Climate-related changes further intensify these pressures. Rising temperatures in polar and high-altitude regions are accelerating glacier melt, altering the timing and quantity of freshwater flow into rivers. As these natural water reserves decline, ecosystems adapted to stable seasonal water inputs face increasing stress.

Together, groundwater depletion, water pollution, irrigation-driven overuse, and climate-related changes make unsustainable water management a significant driver of biodiversity loss across freshwater and terrestrial ecosystems.

#7 Climate change

Climate change is a major driver of biodiversity loss because it alters environmental conditions faster than most species can adapt. Rising temperatures, shifting precipitation patterns, and an increasing frequency of extreme weather events are transforming ecosystems that had remained relatively stable for thousands of years.

Species evolve gradually in response to long-term environmental patterns. When temperature and rainfall regimes change rapidly, these finely tuned relationships are disrupted. Plants may flower outside optimal periods, insects may emerge when food sources are unavailable, and migratory species may arrive in habitats that no longer provide suitable conditions.

One of the most significant drivers of climate-related biodiversity loss is ocean warming. As seawater absorbs excess heat and carbon dioxide, marine conditions change, altering habitat structure and ecological interactions. Warming oceans also affect currents and nutrient distribution, reshaping marine ecosystems across large geographic areas.

On land, rising temperatures and prolonged drought increase the frequency and intensity of wildfires. Although fire is a natural component of some ecosystems, current fire regimes exceed historical patterns. Repeated burning alters vegetation structure, soil properties, and habitat availability, changing the ecological conditions many species depend on.

Climate change also drives biodiversity loss through its effects on freshwater systems. Reduced snowpack, earlier snowmelt, and altered rainfall patterns change the timing and volume of water flowing through rivers and lakes. These hydrological shifts modify habitat conditions and place stress on species adapted to stable water regimes.

In polar and high-altitude regions, rising temperatures are accelerating ice melt. As ice-dependent habitats shrink, species adapted to these environments lose critical ecological niches. Newly exposed land and water also alter species interactions, further reshaping local ecosystems.

Climate change does not operate in isolation. By interacting with habitat loss, pollution, and overexploitation, it intensifies existing pressures on ecosystems and accelerates biodiversity loss across terrestrial, freshwater, and marine environments.

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