BIOL1020 Lecture 10 - Threats to Biodiversity

The primary threat to Earth's biodiversity is caused by a combination of increasing human population and resource exploitation, which exacerbates environmental degradation and threatens species survival. This escalating crisis can be traced back to the growth in the human population correlating with an unsustainable extraction of resources from the environment, which not only negatively impacts biodiversity but also diminishes human access to essential ecosystem services such as clean air, water, and food security.

Human Population Growth

Over the past few decades, the frequency at which the Earth's population has added a billion people has drastically changed, leading to rapid population increases that strain our natural resources. Since 1959, the global population has surged from 3 billion to over 7.9 billion today, a growth rate that places immense pressure on ecosystems around the world.

Major Threats to Biodiversity

  1. Habitat Loss
    Habitat loss is one of the most detrimental threats to biodiversity, directly linked to human population growth and resource utilization. It is driven by activities such as agriculture, urban development, and mining, which lead to the conversion of natural environments into man-made spaces.

    • Technological modification of environments through infrastructure development and land-use change profoundly displaces natural ecosystems.

    • As habitats are eliminated, species that depend on these settings face increased risks of extinction, leading to reduced biodiversity and compromised ecosystem stability.

  2. Overharvesting
    Overharvesting is predominantly driven by population growth, which leads to increased demand for resources, particularly affecting marine and freshwater species through practices such as overfishing and illegal fishing. This has resulted in significant declines in fish populations and the collapse of several fisheries that were renowned for their productivity for centuries.

    • Increased mechanization and techniques in fishing have further exacerbated the problem, rendering traditional, sustainable practices almost obsolete.

  3. Invasive Species/Exotic Species
    The introduction of non-native species to ecosystems, whether intentionally or accidentally, poses a direct threat to indigenous species and habitats. These invasive species often outcompete native species for resources and can cause significant shifts in ecosystem functions.

    • Management of invasive species is essential for conservation efforts to restore balance within ecosystems.

  4. Climate Change
    Climate change has profound effects on biodiversity, altering habitats and the distribution of species. The rise in global temperatures influences weather patterns, affecting plant and animal life cycles, migration patterns, and food availability.

    • Increased frequency and intensity of natural disasters, such as floods and wildfires, further threaten biodiversity.

Habitat Loss Explained

Habitat loss has escalated significantly since the latter half of the 20th century, greatly affecting species diversity worldwide. When habitats such as forests, wetlands, and grasslands are destroyed, entire populations and species are at grave risk of extinction, especially if their ecological niches are irrevocably altered.

  • Notable examples include the deforestation of tropical rainforests in Indonesia and the Amazon, which are crucial for global biodiversity.

Example: Sumatra

Sumatra is home to critically endangered species such as orangutans (Pongo abelii, Pongo tapanuliensis) and Sumatran elephants (Elephas maximus sumatranus), along with various other endangered species, including the Sumatran tiger (Panthera tigris sumatrae). Approximately half of Sumatra's forests, crucial for these species' survival, have been destroyed due to palm oil plantations, logging, and agricultural expansion.

Example: Borneo

Borneo faces a similar loss of habitat, remarkably affecting orangutans (Pongo pygmaeus), which are critically endangered due to the continuous reduction in forest cover. This habitat destruction is significantly exacerbated by the aggressive expansion of logging and oil palm plantations, further driving the region's biodiversity crisis.

Impact of Habitat Loss on Ecosystems

The ramifications of habitat loss extend beyond forests to aquatic environments; rivers, streams, and wetlands suffer significantly from land development and infrastructure projects like dams and channelization. For instance, 91% of rivers in the U.S. have experienced altered flows due to human modifications, demonstrating how land development can disrupt entire aquatic ecosystems and lead to dramatic declines in fish and amphibian populations.

Overharvesting

Overharvesting poses a significant threat to various species across all ecosystems, particularly in aquatic environments, where practices such as bottom trawling and illegal fishing lead to fishery collapses and devastating declines in biodiversity. A notable case is the Atlantic cod fishery, which was once highly productive but has since become unsustainable due to modern fishing technologies and practices. It is currently classified as vulnerable (VU) by the International Union for Conservation of Nature (IUCN) due to overexploitation.

Economic Factors in Fisheries

Fisheries are often treated as a common resource which leads to what is known as the “tragedy of the commons.” Fishers frequently lack incentives to conserve fish stocks, often leading to overexploitation.

  • As biological growth rates of fish populations may be slower than the profits achievable from fishing, only intensifying this unsustainable cycle.

Example: Whales and Sharks

Whale populations, particularly the North Atlantic Right Whale, are critically endangered (CR) due to their slow reproductive rates and extensive hunting. Meanwhile, species such as the Bull Shark are listed as vulnerable (VU) due to overfishing threats, while other species like the Nassau Grouper are classified as critically endangered (CR).

Global Fisheries Status

According to the FAO Annual Report, trends in marine fishery stocks indicate that many are biologically unsustainable as of 2021, highlighting the urgent need for global fisheries management and reform.

Coral Reefs

Coral reefs, essential for global biodiversity, face significant threats from overfishing, climate change, ocean acidification, and pollution. These ecosystems are home to numerous species, some listed as vulnerable (VU), that rely on coral habitats for survival.

Trade and Personal Aquaria

The personal marine aquarium trade frequently utilizes wild-caught organisms, contributing to population declines. This indicates a pressing need for sustainable harvesting practices within the pet trade. The threat of overharvesting extends to terrestrial environments as well, where hunting for food, sport, and illegal trade increases human demand and rapidly depletes various species.

Conclusion

The interplay between habitat loss, overharvesting, climate change, and invasive species is critical in assessing and developing effective strategies to safeguard biodiversity. Coordinated action is required at both international and local levels to mitigate these threats and protect biodiversity effectively for future generations.