Threats to biodiversity

5 major threats to biodiversity(ranked)

1. Habitat loss and degradation

2. Over exploitation

3. Biological invasions

4. Climate change

5. Pollution

Habitat loss

also threatens aquatic ecosystem

deforestation

Degrades habitats

Agriculture removes soil nutrients->reduction in primary productivity

Nutrient addition->eutrophication

Fire often used to clear land->CO2(carbon sink -> source)

Fragmentation

Deforestation & development lead to habitat fragmentation

Smaller habitat fragments = Higher extinction probability

-Creates edge habitat that favors generalist species

-Species specialized in forest interior decline (often large predators)

Patches may function like a metapopulation, but dispersal can be dangerous

Urbanization

leads to loss of species across all taxa & trophic levels

Many species are tolerant of urbanization but most are not

leads to global biotic homogenization of ecological communities

Over exploitation

Occurs when harvesting(removal) of wild organisms at rates exceeding the ability of their population to persist

Not just food: many species poached for economic value

Overexploitation most severely impacted

Species w/ restricted habitats (endemics, island species)

Large organisms w/ low reproductive rates

habitat loss and degradation most severely impacted

Large-bodied, wide-ranging, specialist, migratory species, endemics

Fishing down the food web

As fish stocks of top trophic levels (predatory fish) decline...

fisheries are now fishing lower trophic levels

Invasive Species

Introduced species that have a negative ecological impact on native species

-Outcompete native species for resources or habitat

-Often cause economic harm

-May consume native species

-Can introduce pathogens to naïve population

Introduced species

moved (intentionally or accidentally) from native range to a new region by humans

invasive species most severely impacted

ground-nesting birds & small mammals

poor competitors

specialists & endemics

Human-Wildlife Interactions

Anthropogenic changes force species into regions where they have closer contact with humans leading to conflict & disease

threats to crops, property, livestock, & human safety—lead to persecution & decline

¾ of emerging human diseases are zoonotic diseases

zoonotic diseases

infectious diseases of animals that can cause disease when transmitted to humans

Transmitted by direct or indirect contact, or an intermediate

species (vector)

pose risks to both health & economic stability

wildlife disease spread

Humans unintentionally spread wildlife disease

-Organisms become more susceptible to disease in degraded

ecosystems

-Habitat loss & fragmentation alters abundance and dispersal of pathogens and their hosts