Topic 4 Conservation and Biodiversity

4.2 Evaluating Biodiversity and Vulnerability

Factors that Lead to Loss of Biodiversity

• Introduction of alien species• Overharvesting• Islandisation (Fragmentation)• Loss of habitat• Pollution

Some of these may occur naturally, some are purely anthropogenicCan you think of some that are not anthropogenic?Humans are having a big effect on the least resilient ecosystems

Non-anthropogenic disturbances

• Wild fires• Movement of plates (leading to change in

local climate)• Volcanic eruptions• Meteorite strikes• Changes in orbit of the Earth and its tilt (lead

to regular changes in climate)

Why are rainforests vulnerable?• They are not resilient to disturbance• They occur close to the equator where conditions

are stable (they have evolved in stability)• They have high biodiversity often with rare

species• Their resources (or land) are in high demand (eg.

for wood, soya, beef, biofuels)• Succession takes a very long time• They have thin, nutrient poor soils which are often

washed away once root systems are destroyedCoral reefs are the only other ecosystem with comparable biodiversity

Biodiversity Hotspots• Rainforests are thought to contain up

to 50% of all the species on Earth• Many contain biodiversity hospots

(where there are large numbers of endemic species)

• Another famous hotspot is Feynbos near CapeTown

• This is the area of a few football fields and is home to 2000 species of flowering plants, many of them endemic

Green Politics• Formally organised political parties based on the ideology

of environmentalism• Green Parties exist in over 90 countries and there is Global

Green Alliance• Many mainstream political parties now higlight ‘green

issues’• Green parties often have an ant-capitalism slant as

capitalism is often seen as driving environmental damage• In Mexico the PVEM allied itself with the PAN and was

instrumental in bringing Calderon to power. In 2012 it allied itself with Peña Nieto and the PRI. Is green politics therefore opportunistic? Does it have to be?

Mass Extinction Events

?

Mass Extinctions (5 events)• Ordovician-Silurian (439 mya)

– A drop in sea levels due to glaciers forming, followed by sea-level rise as they melted – 57% of all genera became extinct

• Late Devonian (364 mya)– Cause currently unknown – 50% of genera became extinct

• Permian-Triassic (251 mya)– Possibly due to asteroid impact– 83% of genera became extinct

• End Triassic (214 – 199 mya)– Due to increased volcanic activity on a global scale – 48% of genera became extinct

• Cretaceous-Tertiary (65 mya) – Asteroid impact in the Gulf of Mexico that ended the dinosaurs – 47% of marine genera and 18% of terrestrial genera became extinct – The mammals filled the niches vacated by the dinosaurs

Mass extinctions

• On average they occur about once every 100 million years – (the last was 65 mya)

• Nobody knows the number of species on the planet – (its somewhere between 5 and 100 million

species)• How can we make estimates of the number of

species on the Earth?e.g. Chemical fogging techniques

The Sixth Mass Extinction Event?

• Mammal species on average last 1 million years• There are about 5000 known mammal species• Therefore background extinction rate is exivalent to the loss

of one mammal species every 200 years on avarage• In the past 400 years there have been 89 mammal species

extinctions and 169 species are currently critically endangered

• This extinction rate is 45 times the background rate• Are we therefore currently living through the sixth mass

extinction event? What is causing it? Is it just affecting mammalian species?

Questions

1. List 5 factors that lead to loss of biodiversity

2. Why is rainforest particularly vulnerable?

3. How many extinction events have there been? What were the causes? How do the first 5 differ from the possible sixth?

4. Why do biologists have difficulty estimating current rates of extinction?

What makes some species prone to extinction?

1. Small population size and small habitat size

Case study:The slender-billed grackle (Cassidix palustris)• It only inhabited Valle de Mexico and Toluca

Valley in small numbers• It became extinct due to habitat loss and draining

of marshland• The last one was recorded in 1910

What makes some species prone to extinction?

2. Specialisation

Case study:Giant Panda (Ailuropoda melanoleuca)• Dependent on bamboo although it is in

order carnivora (it will switch to other food sources but very rarely)

• It is endangered due to habitat loss (loss of bamboo forest)

What makes some species prone to extinction?

3. Low reproductive capacity

Case study:Black Rhinoceros (Diceros bicornis)• Gestation period of 15-16

months and only give birth to one calf

• It is critically endangered and one sub-species, the western black rhino was declared extinct in 2011

What makes some species prone to extinction?

4. Poor competitors

Case study:Dodo (Raphus cucullatus)• Flightless and slow-moving• Unable to protect itself against the

pressures of human hunting and introduced species (eg pigs)

• The last one was recorded on Mauritius in 1662

What makes some species prone to extinction?

5. Prone to hunting by humans (value to humans)

Case study:Blue Whale (Balaenoptera musculus)• Fairly easily hunted and provide huge

quantities of meat and blubber• Now critically endangered in the Arctic and

have threatened status in the Pacific• Recovering since they received protection

in 1955 from the International Convention for the Regulation of Whaling

What makes some species prone to extinction?

6. Altruism

Case study:Carolina Parakeet (Conuropsis carolinensis)Monogamous pairs that live together (therefore often hunted together) and come to each others aid if threatened• Last one killed in the wild in 1901• Last captive pair (Incas and Lady Jane) died in

1917 and 1918, respectively

What makes some species prone to extinction?

7. ClumpingCase study:Passenger pigeon (Ectopistes migratorius)Native to North America. Lived in large groups for protection and to find food. When split into smaller groups, the population was no longer viable and declined further• Flocks were estimated to exceed 3 billion

individuals in the early 1800s• Their habitat was fragmented and they provided

a cheap and plentiful food source (especially for slaves!)

• Last one (Martha) died in Cincinati Zoo in 1914

What makes some species prone to extinction?

8. Position in the food chain

Case study:Bald Eagle (Haliaeetus leucocephalus)Top predators are always rare due to the loss of energy through the food chain. They are also vulnerable to the bioaccumulation and biomagmification of non-polar toxins in the food chain• Bald eagles were subject to hunting, habitat loss and

the effects of a number of toxins • By the 1960s there were less than 500 nesting pairs

in the US and Canada by the 1960s• They were especially vulnerable to the effects of

DDT (banned in the US in 1972 and Canada in 1973)

Determining Conservation Status

• This is carried out by the International Union for the Conservation of Nature (IUCN)

• Their red list is a constantly updated list of threatened species

• To compile this they take into consideration:– Population size– Reduction in population size– Number of breeding individuals– Size of habitat and degree of fragmentation– Quality of habitat– Probability of extinction

Questions

• Make a list of a number of species currently on the IUCN red list

• Link each of the species directly to one of the eight reasons that make a species prone to extinction

Case Studies: Extinct• Tasmanian Tiger (Thylacinus

cynocephalus)• Originally extant in Australia, New

Guinea and Tasmania• Habitat: grassland and Eucalyptus

forest• Nocturnal, top predator (but was in

competition with many other species such as the Tasmanian Devil)

• Hunted to extinction (largely by farmers to protect livestock)

Case Studies: Critically Endangered• Black Rhinoceros (Diceros bicornis) – There are 4

subspecies • Largely Kenya and Namibia, East Africa• Habitat: Grassland and desert• Hunted close to extinction (European sport

hunters, farmers protecting crops, poachers)• At the start of the 21st century there were less

than 50• There are now around 4 500• Protection:

– Existing protected areas have been established and old ones expanded

– Improved security to deter poachers– International law enforcement has been improved to

restrict the sale of rhino horn– Ecotourism is an expanding and lucrative market in

Africa

Case Studies: Back from the Brink• Bald Eagle (Haliaeetus leucocephalus)• All of mainland USA and Canada• Habitat: Lakes, marshes and coast• Came close to extinction due to hunting,

habitat destruction and pesticide poisoning (especially DDT)

• By the start of the 1960s there were less than 500 nesting pairs. There are now around 10 000 pairs

• Protection:– DDT outlawed in the USA in 1972 and

restricted in Canada in 1973– Hunting was prohibited in 1940, but ilegal

hunting continued to some extent

Case Studies: A Threatened Area• The Great Barrier Reef• Stetches for 2300 km along the Queensland Coat• Ecological, socio-political and economic pressures• Ecotourism is helping conservation but in some ways

hindering it• There is a serious problem of terrestrial runoff as the coast

becomes more industrially and agriculturally developed• Rising sea temperatures are a problem since corals survive

within a very narrow band of temperature. Climate change may also cause fish migration

• The Australian government allows limited fishing and trawling within the national park which can be destructive

Questions

1. Do some species have more rights to conservation than others. How can this be justified?

2. Do pandas have a greater right to conservation than lichens?

3. Do pests have a right to be conserved?