Biodiversity L4

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  • Created by: maya
  • Created on: 15-05-17 00:46

Current threats to biodiversity pt1

Biodiversity loss schemes and policies we make to reduce loss 

how many species are there and how many are we losing?

what are the main drivers of biodiversity loss?

focus is on tropical deforestation and mechanisms we use to discourage people from deforestation 

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One of things that affects biodiversity...

Government.... voting

1) EU environmental regulations
2) Biodiversity offset schemes
3) Climate change policy
4) Renewable energy schemes
5) Forest conservation 

POLITICS - we have many  policy schemes that decide what sort of environmental regulations we practice  - domestically and globally these are approached

 - this effects biodiversity and biodviersity loss 

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Biodiversity on Earth

Approx. 1.8 million species have been described

Estimated species not described:
estimated species richness 8.9million anthropods 
1 million bacteria 

amount of species that remain undiscovered- estimates suggest lots of species which remain unknown-  reality is we're describing species all the time

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New species all the time

Some species were found in markets, being exploited by humans before we gave them names 

(Vermeulen et al. 2014)

Perentages of missing plant species predicted to occur across regions: 

The most prominent areas were those areas with highest biodiversity- biodiversity hotspots- central America, central Asia- these biodiversity hotspots of species we think are there (don't know about) as well as ones we know

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How many species have we lost?

Animals 726 species.

Plants 90 species

Annual species loss between 0.27% - 0.63%

This is significant because we know we're losing species at an alarming rate- this varies against species and taxa

- in reality it's  likely the level of species lost including the species that are undiscovered is a lot higher

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MEA 2005

"Over the past 50 years, humans have changed ecosystems more rapidly & extensively than in any comparable period of time in human history"

"This has resulted in a substantial loss in the diveristy of life on Earth" MEA 2005 

This is the initiative to understand stock and relationships to human wellbeing and drivers causing that loss
- looking at biodiversity and assessment of current biodiversity of earth - living in period of a biodiversity criss

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Millennium Ecosystem Assessment

Current extinction rates estimated to be X100 greater than background "geological rates" and predicated to increase strongly during this century.

10-20% of mammal, bird & amphibian species currently threatened- extinction. 

gone significantly over the fossil record ( by x100) shows us our natural baseline rates of biodiversity loss.

this forms a motivation for why biodiversity LEC145 needs to exist

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Main drivers of biodiversity loss

Direct / Proximate
-most severe, responsible for changes we're seeing today

Habitat loss and fragmentation
Climate Change 
Over-exploitation
Pollution
Invasive species

Underlying 
Policy/institutional factors
Economic factors (underlyng cause roads- fragmental) 
Cultural factors
Demographic factors 

We have to focus on these two because if we only focus on the direct cause - we are not looking at underlying drivers- need to look behind that- more than meets the eye
Not all species equally vulnerale or vulnerable to the same drivers

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Direct/[proximate drivers of tropical deforestatio

Infrastructure extension

1) Transport (roads, railroads, etc)

2) Markets (public & private, e.g. swmills)

3) Settlements (Rural & urban)

4) Public Service (Water lines, electrical grides, sanitation etc)

5) Private company (hydropower, mining oil exploration)  

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Agricultural expansion

- Permanent Cultivation (large-scale vs smallholder substence vs commercial)

- Shifting Cultivation (slash & burn vs traditional swidden) 

- Cattle Ranching (large-scale vs smallholder)

-  Colonisatiion (inc. transmigration and resettlement projects) 

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Direct/[proximate drivers of tropical deforestatio

Wood extraction

1) Commercial (State run, private, growth coalition etc)

2) Fuelwood (mainly domestic usage)

3) Polewood (mainly domestic usage)

4) Charcoal production (domestic & industrial uses

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Underlying drivers of tropical deforestation

Demographic  factors

  • Natural Increment (Fertilitity, mortality)
  • Migration (in/out migration)
  • Population Density 
  • Population Distribution
  • Life Cycle Features 
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Underlying drivers of tropical deforestation

Economic factors

  • Marker Growth & Commercialisation
  • Economic Structures
  • Urbanisation & Industrialisation
  • Special variables (e.g. price increases, comparative cost advantages) 
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Underlying drivers of tropical deforestation

Technological factors

  • Agro-technical Change (in/extensification) 
  • Applications in the wood sector (e.g. mainly wastage)
  • Agricultural production factors
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Underlying drivers of tropical deforestation

Policy & Institutional factors

  • Formal Policies (e.g. on economic development, credits)
  • Policy Climate (e.g. currption, mismanagement)
  • Property Rights (e.g. land races, titling)
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Underlying drivers of tropical deforestation

Cultural factors

Public Attitudes, values and Belief (e.g. unconcern about forest, frontier mentality) 
Individual and Household Behaviour (e.g. unconcern about forests, rent-seeking imitation) 

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Other factors (underlying causes)

  • Pre-disposing environmental factors (soil quality, forest fragmentation etc)
  • Biophysical drivers (Triggers eg. droughts, fires, floods, pests
  • Social Trigger Events (War, revolution, social disorder, abrupt policy shifts/displacements, economic shocks 
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Drivers of tropical deforestation (Direct and unde

Wood extraction
Agricultural expansion
Infrastracture extension

Policy and Institutional factors 
Other factors 
Cultural factors 
Technological factors
Economic factors 
Demographic factors 

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Main drivers of biodiversity loss

Habitat loss and fragmentation

  • Loss of habitat total area (not lost in homogenuous pattern- what it does to resulting ecosystem can vary- don't necessarily lose the 25% as a chunk - infact we can lose that 25% in a lot of different spatial figurations)
  • Increased edge effects  (edge effects-  means that we're increasing the amount of edge periphery of that area relative to the area of the habitat itself.  This affects species which live in the shade, such as bluebells. If we increase the edge effect then more sun gets in which will cause there to be less bluebells because we're changing the characteristics of the site. 
  • Increased path isolation 
    Decreases path size 
    (this affects ability of mating encounter., seed dispersal- isolation)
  • Habitat loss and fragmentation - LIID 
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Why do small & isolated fragments have less specie

-Large species contain a higher variety of habitats. (greater range heterogeneity - encompasses broader range of species)

- Large fragments contain both common and rare species. (fragmented habitats tend to include more common species with less rarer populations )

- Large fragments have larger populations, less likely to go extinct. 

- Isolated fragments are less likely to be colonised if a species is lost (species have limited mobility- unable to colonise if lost, which menas a native species may not be able to return)

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Example: Mountain forest mammals in SW USA (graph)

graph below shows that as patches become more isolated there is a decrease in the number of species found in those plots 

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example: Tropical forest in Madagascar

Today only 10% of the tropical rainforest remains 

  Causes:

  • Timber extraction
  • Forest conversion to pasture for grazing 

    Consequences

    Human influence on Madagascan fauna in the past has caused many species to become extinct since human arrival. 

    Historical loss of species as a result of change by humans discovery and arrival
    Madagascar lost a huge number of giant  lemurs and other megafauna- now extinct from Madagascar. 

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Tropical forest in Madagascar - consequences cont.

Human influence on Madagasca fauna in recent decades -
this is only related to known species Madascar has been poorly explored and has a wide variety of endemic species - there are many undiscovered species in Madascar - actual rates will be higher. 

9.1% of species have been committed to extinction from deforestation between 1950 and 2000

.Potential human influence on Madascan fauna in the future: 

Total species: 200,000 (75% endemic) exist nowhere else in the world, no one has done an estimate, we dont know if the populations are still viable 

Total species ; 200,000 (75% endemics)
Critically endangered: 37
Endangered: 88
Vulnerable: 137

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example: Semi-natural habitats in Britain

Semi-natural habitats have reduced dramatically during the last 50 years.
In some cases, only 4-5% of the original habitat remains 

Causes 

Agricultural Intensification 

  • Removal of hedgedrows to create larger fields. (This eats up habitats. aim: larger fields = smaller hedgedrows).
  • Ploughing up closer to the edge of the field to increase the planted area. // Industrial and mechanical, more sophisticated technology - means that we can harvest right at the edge. This has implications for soil & organisms that could grow there, scraped away - not able to colonise here.
  •  Drainage: dries out wetter areas to increase total area for production (growing rates of drainge in the land changes the hydrology of this area- and the ability of frog species to spawn in the spring. 
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example: Semi-natural habitats in Britain

Consequences 

Butterflies,birds and plants have all declines n the UK during the last 40 years. 

When we create altered habitats its iimpact on individuals is variable despite having negative effects on populations - so species can increase if they like these altered characteristics yet these are habitat generalists, tend to be commoner not rarer. 

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Main drivers of biodiversity loss - OVEREXPLOITATI

Human harvest of a species at a faster rate than it reproduces (this is what over-exploitation refers to) 

Pets: seahorses, tropical fish, birds

• Ornamental plants: orchids, cacti

• Medicine: rhinoceros horn, many plants

• Cultural artefacts: skins, ivory

• Recreation: trophies

• Food, both subsistence and luxury: deer, fish caviar

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Over-exploitation explained

We can set quotas to be sustainable- decide how much we can afford to harvest,but this requires a lot of info about the species

  • harvest more females/males? higher percentage of adults?
  • only juvenies?
  • This requires good regulations and enforcements - which does not characterise most of the world more often than not - we're harvesting more than the population can sustain: 

1) Pets- extends into ornamental plants- largest threat to cacti species is human harvest for collectors who want them in their gardens- one of the largest drivers of species loss.

2) large medicinal trade- rhinoceros horn being used in medicine - perceived values of these resources- people perceive it has a certain value so they harvest it. Plants and herbs in contemporary medicine- native parts used in the world  are herb-based medicine.

Fashion: fur in coats-
3) recreation- harvest of trophies & species for food- reflection of luxury presence- urban consumers in a city centre- maybe international consumers wanna eat caviar- large continuum between need and greed or subsistence 

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Example: Historical cases of over-exploitation

Woolly mammoth went extinct 8000 years ago

Dodo extinct since 1674

Great auk extinct since 1854

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Over-exploitation of ornamental orchids

Causes: 

Modern extinctions (targeted harvest on species)
Local extripations
Global demand as species becomes more rare and desirable

Paphiopedilum canhi Aver. & O.Gruss 2015 listed critically endangered 
(1 population, <10 mature individuals)

Consequences:

  • Changes to population structure
  • Genetic erosion 
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Over-exploitation of fisheries

Consequences: 

  • Changes in community structure
  • Trophic cascades 

    28% are overexploited
    3% are depleted 

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Main drivers of biodiversity loss

Invasive Species 

Invasive species: any exotic species that outcompetes, displaces or eradicates any native species.

Exotic species: any species living outside its native geographic distribution
(exit to the Outside- exOtic) 

All invasive are exotic but not all exotic become invasive.

Native range: the geographic range a species will occupy without human interference.

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Invasive Species

- not linear lots of ways they can come about.

How do they move? 

Accidentally introduced by people:

• Norway and Black rats: stowaways on ships
• Pathogens and diseases: rabies virus
• Plant seeds in packing materials: many European plants to Australia and New Zealand 

- Shipping containers- brought beetles from Asia into the US- these beetles affect a number of different species 

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Invasive Species

Deliberately introduced by people:

• Pest control: Cane toad in Australia (historically, didn't understand ecological consequences of these species) 

• Recreation: Grey Squirrel in UK, ornamental plants in Hawaii (now have displaced native red squirrel- outcompetes it) 

• For food: Crayfish in Europe

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Invasive Species

Deliberately introduced by people:

• Pest control: Cane toad in Australia (historically, didn't understand ecological consequences of these species) 

• Recreation: Grey Squirrel in UK, ornamental plants in Hawaii (now have displaced native red squirrel- outcompetes it) 

• For food: Crayfish in Europe

Expansion naturally because of human changes to the environment:

• Construction of canals: Parasitic sea lamprey (fish) into the Great Lakes (displaced native flora, sea lamphrey fish- created canals where water is disconnected which allows these fish to move in) 

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Invasive Species

Why do they become invasive?  Invasive species are generalists have a lot of characteristics which allow them to be invasive

• High dispersal ability

• High reproductive potential (rhododendron) 

• Broad ecological niches (not hghly specialised)

• Lack of enemies in the area of invasion 
In native ranges a lot  of these species have native predators who keep their populations in check- but when they're introducted into new areas their predators are not essentially introduced so we lose the natural biocontrol.

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Example: Endangered white-headed duck

Consequences:

• Hybridization with native species

ontemporary duck this is under external threat from:
deforestation,
wetland and over-hunting.
one of the newest concerns is that it's begun to hybradise with another species
- ruddy duck - the white-headed duck is breeding with this species- fundamentally changing its genetics.the ruddy duck is a free species, willing to breed desperate- willing to breed across species 

White-headed duck is easy causing hybridisation 

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UK rhododendron

rhododendron in the UK is beautiful and strong used a root stock -
get a plant that could withstand the climate.
problem is that the rhododendron becomes dominate- particularly in oak woodland

it takes over and creates such a heavy understory that there are no seedlings which grow under it-
native blueberries do not grow under rhododendron
 - less moisture- fundamentally changing wootland structure
causes rain to run down and help plants get enough mositure. changes how these forests look. t
he sap of this can cause problems to humans and its skin.

the nectar is toxic to honey bees-another pressure driving on them 

Rhododendrum seen in Lancaster Woodland - no small shrubs near it or bluebells 

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Example: Cane toad introduction to Australia

Cane toad very aggressive reproduces very fast introduced to deal with pest control in sugar canes- dominates other areas - moving very quickly. it's a highly toxic species- produces hallucinogenic effects- some people lick this- when another species bites into it and it produces its toxin it kills them. out-competing other species eating their young- broad range of species have been effected by this.

Consequences:

  •  Extinctions of native species through competition or predation
  • Population declines of native Australian reptiles:

• Lizards: Varanus mertensi, V. mitchelli,V. panoptes

• Snakes: Pseudechis australis Acanthophis antarcticus,

• Crocodiles: Crocodylus johnstoni

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Example: The Nile perch in Lake Victoria

Fast growing- eats a lot of food- fundamentally shifted food web and nutrient cycling in that ecosystem

Consequences:

Extinctions of native species through competition or predation

• Disruption ofecosystem’s structure and function

• >200 fish species extriptated

• Altered food wet

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Part 2

Main drivers of biodiversity loss;

Discussed:
Habitat loss and fragmentation
Over-exploitation
Invasive species

Part two is.. 

• Pollution (Pollution and global climate change- direct causes) 

• Global Climate Change

• Uderlying drivers (particularly salient - requires a range of diff things to stop impacts)

• Synergistic effects of different factors

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References

• Required

– Geist, H.J., Lambin, E.F. 2002. Proximate causes and underlying

driving forces of tropical deforestation. BioScience 52:143-150.

URL: https://tinyurl.com/lk5rxuo.

– Sodhi, N.S., Erlich, P.R. (Eds.). 2008. Conservation Biology for

All. Oxford University Press, Oxford. See pages 27-35, 73-76,

107-115. URL:

https://conbio.org/images/content_publications/

ConservationBiologyforAll_reducedsize.pdf.

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