Lecture 14 - Keystone Species and Biodiversity Loss

These flashcards cover key concepts related to keystone species, biodiversity loss, and international environmental law. They are designed to help reinforce the major points discussed in Lecture 14.

What is a keystone species?

A keystone species significantly influences its ecosystem's structure and function more than its abundance suggests; their presence is vital for maintaining ecosystem stability.

Impact of keystone species removal?

Removing a keystone species causes cascading detrimental effects, leading to drastic changes in species composition, altered food webs, and a significant degradation or even collapse of ecosystem functioning and biodiversity.

Example of a keystone species role?

The starfish (Pisaster), a keystone predator in intertidal zones, controls dominant mussel populations. Its absence leads to mussel overgrowth, outcompeting other species and causing a dramatic crash in overall biodiversity.

Impact of sea otter removal on kelp forests?

Removing sea otters (keystone predators) allows sea urchin populations to explode. These urchins then overgraze and destroy kelp forests, transforming them into barren 'urchin barrens' and severely reducing marine habitat and food sources.

Large-mouth bass as a keystone species?

Large-mouth bass are keystone predators that control algae-grazing minnow populations. By doing so, they indirectly prevent overgrazing of algae in freshwater, maintaining balanced algal communities and good water quality, averting disruptive algal blooms.

Define 'landscape of fear'.

The 'landscape of fear' describes how a predator's presence or perceived risk of predation significantly alters prey behavior. Prey reduce foraging and movement in risky areas, thereby impacting their spatial distribution, vegetation, nutrient cycling, and broader ecosystem dynamics.

Major direct threats to biodiversity?

The four main direct threats to global biodiversity are:

1. Habitat loss/change: Destruction, degradation, and alteration of natural habitats.

2. Climate change: Altered weather patterns and extreme events.

3. Overexploitation: Unsustainable harvesting of wild populations.

4. Invasive species & disease: Harmful non-native species and pathogens.

Largest driver of biodiversity loss?

Habitat loss and change is the single largest and most pervasive driver of biodiversity loss across most terrestrial, marine, and freshwater ecosystems, including destruction, fragmentation, and degradation.

Define habitat fragmentation.

Habitat fragmentation occurs when a large, continuous habitat is broken into smaller, isolated patches by human land use (e.g., roads, agriculture). This reduces total habitat, increases 'edge effects', and creates substantial barriers to species movement.

Main causes of habitat loss?

The two main causes of global habitat loss are:

1. Increasing human population and consumption, which demands more resources.

2. Major human activities like agriculture, urban development, logging, and mining directly destroying habitats.

Why are human impacts non-local?

Human ecological impacts are non-local because resource consumption and waste production affect ecosystems globally, extending beyond their immediate source. This is driven by global trade, transport, and resource extraction, creating an 'ecological footprint' that crosses all geographical borders.

Benefit of wildlife corridors?

Wildlife corridors connect isolated habitat patches, facilitating gene flow to maintain genetic diversity, enabling population rescue for declining groups, and providing colonization opportunities for species responding to environmental change.

Define 'extinction debt'.

Extinction debt describes species already committed to extinction due to past habitat loss and environmental changes, even if they still exist. These 'doomed' populations face long-term survival impossibility due to factors like reduced habitat, low birth rates, and limited gene flow.

Goals of Kunming-Montreal Biodiversity Framework?

The Kunming-Montreal Global Biodiversity Framework (2022) aims to halt and reverse biodiversity loss, with key targets including:

• Protecting 30% of global land and ocean by 2030.

• Reducing extinction rates significantly.

• Restoring degraded ecosystems.

• Substantially reducing pollution.

• Ensuring sustainable and equitable use of biodiversity.

What was the Montreal Protocol?

The Montreal Protocol (1987) is a landmark international treaty to protect Earth's stratospheric ozone layer by phasing out ozone-depleting substances. It's considered one of the most successful global environmental agreements.

Why are international approaches crucial for biodiversity conservation?

International conservation is crucial because species and ecosystems transcend political borders. Migratory species and global environmental impacts (climate change, pollution) require coordinated, collaborative efforts among multiple nations for effective conservation.

Primary impact of habitat fragmentation on wildlife?

The primary impact of habitat fragmentation is population isolation, which creates barriers to gene flow. This leads to greater susceptibility to inbreeding, reduced genetic diversity, and a higher risk of local extinction due to diminished resilience against environmental changes.

Human ecological footprint & biodiversity loss?

The human ecological footprint measures the productive land/water needed to provide resources and absorb waste. It's relevant to biodiversity loss because human demand often exceeds Earth's biocapacity, demonstrating non-local, globally interconnected impacts that drive habitat loss, overexploitation, and pollution.

Substances targeted by Montreal Protocol?

The Montreal Protocol targeted Chlorofluorocarbons (CFCs) (refrigerants, aerosols) and other ozone-depleting substances (ODS) like halons, carbon tetrachloride, and methyl chloroform. These chemicals caused the destruction of the stratospheric ozone layer.

How does climate change threaten biodiversity?

Climate change threatens biodiversity by altering habitats (e.g., desertification, ocean acidification), causing species range shifts, disrupting ecosystem processes (e.g., phenology), increasing extreme weather events, and potentially leading to widespread species extinctions if adaptation or migration is insufficient.

Define 'overexploitation' as a biodiversity threat.

Overexploitation is the unsustainable harvesting of plant or animal populations beyond their natural replenishment rates. Driven by human demand, this leads to severe population declines and species extinction, evident in overfishing, overhunting, and unsustainable logging.

How do invasive species threaten native biodiversity?

Invasive species are harmful non-native organisms that threaten native biodiversity by: outcompeting natives for resources, introducing diseases, altering habitats (e.g., fire regimes), and disrupting food webs via predation or resource removal, often causing native population decline or extinction.

Define 'edge effects' in habitat fragmentation.

'Edge effects' in habitat fragmentation are ecological changes at boundaries between natural and altered landscapes (e.g., forest next to clear-cut). These include altered light, temperature, wind, increased predation, invasive species, and human disturbance, negatively impacting edge species and reducing viable interior habitat.

Earth's 'biocapacity' vs. ecological footprint?

Earth's 'biocapacity' is its capacity to produce resources and absorb waste. The ecological footprint measures human demand on these resources. When the footprint exceeds biocapacity, it signifies unsustainable consumption, leading to an ecological deficit and environmental degradation.

Primary function of stratospheric ozone layer?

The stratospheric ozone layer's primary function is to absorb most of the Sun's harmful ultraviolet (UV) radiation (especially UV-B and UV-C). This protective shield is vital for all life on Earth, preventing severe damage to DNA, cells, and ecosystems from excessive UV exposure.