Global Change LECTURE 1- The past

How have we negatively impacted other psecies and habitats

1. harvesting themat at a higher rate than their populations could withstand

2. Converting natural habitat to human-dominanted land uses

3. Through tansporting and releasing species to new locations

consequences→ marked incrase in extinction rates

Despite losses and turnover of species

• biology diversity has generally increased over time

• But punctuated by 5 mass extinction events

  → at about 0.1→ 1.8 extinctions per million sepcies yesrs

Humans are super-predators?

• killing far more prey population

• larger bodied species at higher trophic levels

• killing more adults

  → than other predators

OVERAL can cause extinctions due to

1. Outcompeting megafauna

2. Hunting lots of megafauna

3. Affecting habitats: agriculture→ loss of land

4. Other things→ invasive species and disease

5. Causing climate chnage themselves

Consequence of this?

→ The megafauna

• End-Pleistocene/early Holocene extinction of 2/3 species >44kg in mass

→ cause not fully understood

What did this cause?

• substantiaal climatic and vegetation change

→ BUT extinction wave happened at different times on different land-masses

• arrival of sophicicated hunts fit more closely than does climate change

• with this staggered chronology loss

E.g 1 Evidence 1

• End-Pliocene extinction of many African proboscideans

• and large carnivores

→ Coincides with emergence of Homo eretectus

• found there was no loss of smaller species→ therefore cannot be an ecological cause

E.g 2 Evidence 2

• INdianan lake sediments show decline of N American megafauna

  • due to lower counts of spopomiella (large mammal fung fungus)

→ This preceeded the rise of fire and change in vegetation by 1Ky

• Coincided the first signs of people

E.g 3 Evidence 3→ Mass butchering sites in New Zealand

• unequivical evidence that polynesian settles

• responsible for eliminating all 9 spp of moas in 150y

Overall

• global picture confirsms consistently close match

• between timing of megafaunal extinction on different landmasses

→ and the first arrival of people

Confirms that the mass extinction were not due to climate change

because they affected different places at different times

• but the timing do match the migration of humans across the world

• ALSO: supported by the fact the these large animals were not affected by any other past ecological changes

Habitate loss

Loss of habitat due to

1. fire in hunting

2. agriculture

   • 11 independent centres of crop and livestock domestication

→ more dramatic changes as habitats were cleared for food production

shifting cultivation gave way to continuous agriculture

If early yields were low…

• By 1800 farming had already removed large areas of natural vegetetion on almost all continents

Another effect of agriculture?

• rise in CO2 and CH4 emissions

• from irrigated rice production

• → climate heating

Invasive species

• inadvertently and deliberately tansported other species

• relased them far beyong their native ranges

e.g 150 spp in british flora are archaeophytes

• plants introduced by people before 1500 AD

example 2→ Beetles

• Greenlland species of beetles

• introduced by nors settles

Example 3 possums

• People moved several species of cuscus→ large possums

• to islands around New Guinea

• for food

• 23k years ago

Example 4→ alen plants

• now causing problems in Australia

• introduced in the first century

  • folloiwng european arrival

How do invasive species impact native communities? E.g Species from the Red Sea to mediterranean (due to Suez canal)

1. Some outcompete natives→ e.g gold band goatfish

2. parasitise native species→ e.g copepods

3. major ecosystem disruption (dusky spinefish grazing down algal beds and exposing the substrate to colonisation by non-native mussel)

Consequences→ largest hit species

• large bodied vertebrates

• largest trrees

(the rest have changed in abundance)

Impact of affecting larger bodied vertebrates

• They have a larger ecological impact

• So when extinct→ causes even more consequences

  • ecosystems get messed up too!

Case Study 1: Amazon facts

• basin drained by the world’ largest river

• 80% covered by largest and most species-rich rainforest on Earth

Case Study 1: What did the uplift of the Andes do?

1. Amazon used to drain into pacific

2. uplift of Andes blocked it→ vast inland late

3. broke through to Atlantic

Case Study 1: Impact of people

1. End of Pleistocene→ lost most megafauna

   • limited fossil evidence (so not sure why?)

   • ut chronology suggests due to humans

2. Habitat conversion

Case Study 1: 1. What has loss of megafauna led to?

Left several ecological signals

1. Reduction in large-scale dispersal of nutrients (e.g Phosphate)

2. decrease in vegetation openess

3. reduced dispersal of large-seeded fruits

4. forest-wide carbon storage→ trees with bigger seeds→ desnser wood)

Case Study 1: 2. Habitat conversion

Evidence of

• wide spread dom crops

• burning of soil

Suggest

• agriculture was widely practised across the Amazon

Case Study 1: 2. WHere was the agriculture?

• mainly around rivers

• more easonal SW

→ suggests the basin was not extensievly converted

Case Study 1: 2. Agriculture stoppped?

Stopped during the Columbian Exchange

• import or European technologies but also

• exposure to diseases→ small pox, measles, flue, plague

Impact:

1. people died

2. farm abandonment

3. forest recovery (explains why look like not cultivated)

→ OVERAL: decrease in CO2 level→ Little Ice Age

Case Study 1: What happened next?

• Human populations slowly recovered

  But then

• Rubber boom→ fresh wave of colonisation→ meet rapidly rising global demand→ people enslaved for the rubber

Case Study 1: What did the end of the rubber boom cause?

• promoting the rise of wide-scale commercial hunting again

Case Study 2: Mauritius Facts

• second largest of the Mascarenes

• 1000km East of Madagascar

• formerly covered almost entirely by evergreen forest

• → Many birds evolved flightlessness

  • BECAUSE lack of terrestrial mammalian predators

Case Study 2: Dutch party landing→ what they saw

• dodos

• raven parrots

• two species of giant tortoise

• fruit bats

• stange palms

• other pigeons and parrots

• skinks

• geckos

• boas

Case Study 2: Species numbers today?

• 35 out of 69 terrestrial vertebrate left

Case Study 2: Causes of this loss of species

1. Overhunting

   • tortoises, turtles, parrots, dugons and dodos

2. Invasive species

   • pigs (ate turtle eggs, tortoises, ground-nesting birds and dodos)

   • monnkeys (depredated nests in trees)

   • cats (ground nesting birds, young tortoises)

   • rates (probs ate all the snakes and larger skinks)

Case Study 2: Habitat loss?

• Not much forest gone at the time→ so thats why most native vertebrate still there

BUT habitat loss accelerated in Frenech and British rule

• for sugar

  • was resilent to cyclones

OVERALL: 1940s→ <10% native forest remained

Case Study 2: Further impacts?

Further introductions of invasive species

• some used as biological controls of previous invasions

• fledging conservation efforts were weakly enforced

Case study 2: Overall

Impacts

• species loss

• habitat loss

Causes

• Invasive species

• overhunting

• agriculture→ sugar

• More species for biological control of other invasive species

Case Study 3: The great Whales facts

e.g Baleen whales and sperm whales

• largest whales

• hunted for at least 8000y

  • meat

  • oil

  • baleen (for whalebone corests)

  • sspermaceti

Case Study 3: History of whaling

1. First large sclae by the Basques→ hunted across N.Atlantic

   • those that went inshore

2. 1860s better technologies→ cannon-fired explosive harpoon and factory ships

3. Whaling much more efficient and wide ranging

4. 1800→ 3.5 Million whales

5. 1945→ 2.5 Million

→ greater reduction in biomass of arounf 40%

Case Study 3: Why does whaling have a massive impact?

Because they have profound ecological consequences

Case Study 3: Role of whales in ecosystems

Ecosystem engineers→ Whale pump in opposite direction to biological pump

1. Feed at depths

2. produce liquid feaces at the surface

3. rich in N and Fe

4. stimulate planktonic photosynthesis

   • therefore, plankton rely on whales to surive

5. Also move up and down in depths→

   • redistributing large quantities of nutrients via urea

6. Great Whale conveyor:

   • carcasses sink to the seafloor

   • shunting tonnes of C from the surface

   • sustaining highly specialised communites of whale-fall scavaneger