Overview/ Steve Flashcards
Why study ecology
- Wealth- Yellowstone wolves
- Well-being- more diversity healthier
- Ecosystem services- trees prevent flooding
- Self preservation- understand where crops can grow under CC
- Ethical/ philosophical people like knowing they’re there
Utilitarian and none benefits from environment
What are the non- utilitarian benefits we get from the environment
Intrinsic- right if a spp to exist
Extrinsic- value of knowing a species or habitat exists
What are the utilitarian benefits we receive from the environment
Direct- consumptive and none
Indirect- ecosystem services
Option value- use values in the future of this generation
Bequest value- use of values for future generations
What is push pull agriculture
intercropping a cereal crop with a repellent intercrop such as Desmodium uncinatum (silverleaf)[4] (push), with an attractive trap plant such as Napier grass (pull) planted as a border crop around this intercrop. Gravid stemborer females are repelled from the main crop and are simultaneously attracted to the trap crop. Napier grass produces significantly higher levels of attractive volatile compounds (green leaf volatiles), cues used by gravid stemborer females to locate host plants, than maize or sorghum. There is also an increase of approximately 100-fold in the total amounts of these compounds produced in the first hour of nightfall by Napier grass (scotophase), the period at which stemborer moths seek host plants for laying eggs, causing the differential oviposition preference. However, many of the stemborer larvae, about 80%, do not survive, as Napier grass tissues produce sticky sap in response to feeding by the larvae, which traps them, causing the death of about 80% of larvae.[3
striga bad weed
What are the main threats to biodiversity
- Over exploitation
- Agricultural activity
- Urban development
- Invasion and disease
- Pollution
- System modification
- Climate change
Based on most prevalent threats for IUCN red list app
Wayne says OE, invasive species, habitat destruction and modification, over exploitation, and co extinction/chains of extinction
What percentage of birds animal and plant species are on the IUCN red list
More than 80%
Between what years was half of the worlds rainforest cleared
1830-1984
What is the evil quartet
Diamond
- introductions
- habitat destruction and degradation (inc pollution)
- overkill
- chains of extinction
Past human impacts on biodiversity
Much of human history populations have been low and so assumed impacts have been low
Howeerv 150 genera of megafauna were extant 50,000 years ago. 97 gone by 10,000 YA. Can quantify human impacts where human arrival can be dated with relative precision and continental isolation shows clear impact on naive fauna eg australia and n america
Australia late pleistocene extinction
fossil evidence tells us aus had diverse fauna in last 100,000 years. Including large bodied animals.
Fossil record difficult because patchy. Timing of extinctions uncertain and body size difficult to ascertain
Howeerv, evidence suggest Aus and New Guinea lost 55 species of mammals, large birds and reptiles about 45,000 ya
Competing hypotheses for what caused this:
climate change
habitat destruction
overkill
Evidence-
a. climate formerly v variable- cold explain wide spread extinction and size selectivity
b. timing consistent with hunting by humans
North Americas late pleistocene extinctions
Humans arrived later than australia (around 14,000- 12,000 YA). Coincides with ice retreat- bering land bridge- “clovis people” had tools to hunt large mammals
Previously north america fauna similar to Africa. Arrival of people at the same time as extinction of 15 genera of large mammals eg mammoths, smilodon- sabertooth cats, ground sloths (fruit produced by trees thought to appeal to these animals)
Cause of extinction debated but prevailing view is native humans in touch with nature so not overkilling for some reason
Controversial view emerging that N america natives far more abundant than usually acknowledge (pop may have been >1million). Evidence increasing that native people over exploit wildlife resources. Evidence that N America already human dominated and wildlife depauperate before Eu arrival
Pre-industrial humans like not conservationists. Overkill can account for many late Plei extinctions. N American extinctions coincide with arrival of humans. Overall humans and overkill (rather than CC) implicted in most extinctions between late Plei and recent centuries
Pic on phone - Jonson 2009
What are the 2 possibilities with overkill
- blitzkreig - high rapid killing focussed on large bodied spp
- Gradual but unsustainable harvest
Pic on phone ??
Reproductive rate, not large body size, predicts extinction. Implies longterm unsustainable hunting than abrupt focus on large animals
- bigger body = more food for less effort
- high reproductive rates can withstand offtake
Climate in invokes in some areas such as S America
Since 1600 most extinctions attributable to
- introductions eg pig, rats, cats, goats
- habitat destruction
- hunting and extermination
- other
cichlids and lake victoria
had loads of species because various radiations then nile perch introduced as to lake victoria. They grow rapidly, were introduce bc thought they’d be a good fishery fish . Boomed in 80s. Extinction of 100 species in lake in 10 years.
American introductions
American signal crayfish outcompete Uk native white claw bc rapid growth, higher fecundity and predate on juvenile white claw
American mink released by animal rights activists fur farmed. Devastating impact on countryside brought water vole close to extinction. Thought otter could outcompete but they have niche partitioned
15% of floridas reptiles and amphibians exotic species
Grey squirrels to UK Paradox virus
Mountain gorillas suffer from colds and flu that tourists bring
