Biosphere Lecture 6

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World population is growing and is expected to continue to grow during the 21st century Reached
7 billion people in 2011
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Huge areas of land devoted to feeding the human population
(36-40% land area)
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In many areas, almost all net primary productivity (photosynthesis – plant respiration = biomass production) is
‘appropriated’
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Degradation has also reduced the productivity of the
terrestrial biosphere
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Nearly one quarter of the potential productivity of the terrestrial biosphere is used
directly by human kind!
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up to 83% of the
global terrestrial biosphere as being under direct human influence, based on geographic proxies such as human population density, settlements, roads, agriculture etc
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36% of the Earth’s bioproductive surface is
“entirely dominated by man”.
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HANPP
“human appropriation of net primary production,”
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HANPP is
,” is an aggregated indicator that reflects both the amount of area used by humans and the intensity of land use.
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NPP
net primary productivity
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NPP is
the net amount of biomass produced each year by plants; it is a major indicator for trophic energy flows in ecoystems
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HANPP measures to what extent
land conversion and biomass harvest alter the availability of NPP (biomass) in ecosystems. It is a prominent measure of the “scale” of human activities compared to natural processes (i.e. of the “physical size of the economy relative to the containin
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Land use transforms earth's terrestrial surface, resulting in changes in
biogeochemical cycles and in the ability of ecosystems to deliver services critical to human well being. The results suggest that large-scale schemes to substitute biomass for fossil fuels should be viewed cautiously because massive additional pressu
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More than 2/3 of the area of
two biomes and more than half of the area of four other hasd been converted by 1990
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Deforestation
Forests clearance to make space for agriculture Historical loss of forests in Europe & N America Deforestation still ongoing in many areas especially in the tropics Globally, we have lost more than 50% of forests
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Deforestation in the amazon:
Since 1970, 700,000 km2 deforested Cattle ranching Subsistence agriculture
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Deforestation in the south-east asia:
Little rainforest left in many places Continuing deforestation in remaining areas
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United Kingdom context
Coalition Government attempted to privatise England’s woodlands but renounced after public opposition.
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Trump’s golf course near Aberdeen
One of the top five remaining dune habitats in Britain Site of special scientific interest (SSSI) Rejected by local councillors but approved by Scottish government
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Habitat loss and fragmentation
Major threat to biodiversity Can consider issues in the context of island biogeography
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Island biogeography
We can apply theory of island biogeography to habitat loss and fragmentation Smaller the area of remaining habitat, the fewer species survive Greater the isolation of the fragment the fewer species it contains
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Rates of extinction
Loss of habitat is currently the greatest threat to biodiversity Big increase in rates of extinction
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Mammals and birds particularly vulnerable
Since 1600, 59 species of mammals have become extinct = 1.3% of all mammal species Natural rate of extinction should be 1 species per 400 years Rapid loss of vertebrate species
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Some species may be key:
Pollinators Keystone species
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If lose these species, it can set up a cascade of extinctions
If a key pollinator goes extinction, then several plant species may follow If a keystone species like wolves in Yellowstone goes extinction, then can affect the diversity of the whole ecosystem (plants, herbivores....)
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Scale of extinctions
Limited success in protecting biodiversity globally Mass extinction = 75% of all species lost Only happened 5 times in geological history Starting the 6th great mass extinction event?
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The passenger pigeon or wild pigeon (Ectopistes migratorius) is an extinct N American bird. Named after the French word passager for "passing by", it was once the most
abundant bird in North America, and possibly the world. It accounted for more than a quarter of all birds in North America.The species lived in enormous migratory flocks until the early 20th century, when hunting and habitat destruction kill them off
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Species “invasion”
Little egrets first bred in UK in 1996 (Dorset) Now many 100s of pairs, especially in south-west England (800% increase in last 10 years) Now beginning to see cattle egrets as well
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Marine realm
Rising sea temperatures are leading to plankton blooms off Cornwall Attracting basking sharks to south-west England in record numbers New ecotourism in Cornwall Huge number of sightings in recent years
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British seabirds
No longer a high biomass of sand eels in traditional areas Have to shift to eating pipefish Low energy value and can choke young chicks Major declines in populations of international importance Arctic skua population has declined by 57%, kittiwake p
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Polar bears and sea ice
Summer sea-ice extent is declining by 8-10% per decade in the Arctic summer Polar bears are a sea-ice dependent species (ice-obligates
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Climate envelope is the range of climatic conditions that
species is found in
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Change in envelope
Species – Area relationship Overall extinction risk
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Can model the effects of climate change across the world using climate envelope modelling Estimate how many species will go extinct assuming that:
Species can migrate to track climate Species cannot migrate to track climate
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How many species could be lost?
Rates of extinction depend on: Rates of climate change Rates of dispersal (migration) High dispersal and minimal climate change: 9-13% of species go extinct by 2050 No dispersal and maximum climate change: 38-52% of species go extinct by 2050
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Interactions with habitat fragmentation
Climate change is a treat to biodiversity Have to adapt or migrate Ability of plants and animals to migrate to track changes in climate considered very important Habitat fragmentation reduces migration rates,
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Land-use change
Conversion of natural ecosystems to agriculture results in a loss of both plant biomass (especially during deforestation), and soil carbon
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Land-use change releases large amounts of carbon to the atmosphere each year
15% of global anthropogenic CO2 emissions
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United Nations REDD+ scheme (Reducing Emissions from Deforestation and Degradation) is attempting to reduce these emissions The fight against climate change may help
protect forests Conservation bodies are highly sceptical
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Carbon dioxide concentrations now higher than during the
last 700,000 years
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This CO2 dissolves in sea-water and carbonate concentrations decline as a result Corals grow by producing calcium carbonate skeletons As CO2 concentrations rise, grow rates
decline Above 480 ppm erosion may dominate over growth
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Name human influences on the N Cycle
Power Stations, Fossil Fuels, Agriculture and haber-bosch process
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Acidification
When nitrogen oxides dissolve in rainwater they produce nitric acid Contributes to acid rain Major adverse effects on terrestrial and freshwater ecosystems Defoliation Accumulation of toxic compounds
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Eutrophication
Nitrate and phosphate concentrations increase in freshwater systems Enhances growth of algal and weedy plants Out compete other plant species
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When algal and weedy plants die
they decompose consuming oxygen C6H12O6 + 6O2 → 6CO2 + 6H2O Leads to loss of many animal species
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Loss of Biodiversity
More nitrogen and phosphorus alters competition between species Important in grasslands and heaths Fast growing grasses are favoured Overall loss of species
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Card 2

Front

Huge areas of land devoted to feeding the human population

Back

(36-40% land area)

Card 3

Front

In many areas, almost all net primary productivity (photosynthesis – plant respiration = biomass production) is

Back

Preview of the front of card 3

Card 4

Front

Degradation has also reduced the productivity of the

Back

Preview of the front of card 4

Card 5

Front

Nearly one quarter of the potential productivity of the terrestrial biosphere is used

Back

Preview of the front of card 5
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