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BIO234_Animal Conservation and Welfare > Overexploitation > Flashcards

Overexploitation Flashcards

1
Q

What is overexploitation?

A

harvesting a renewable resource faster than it can be produced

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2
Q

What percentage of threatened or near-threatened species on IUCN Redlist are being overexploited and what for?

A

72% (6.241)
For commerce, recreation or subsistence

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3
Q

What did humans implicate the extinction of in pre history?

A

most megafauna
can rapidly drive superabundant species to extinction e.g. passenger pigeon

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4
Q

Why have rates of overexploitation been increasing?

A
  • high human population
  • increased demand
  • advanced technologies for harvesting
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5
Q

When populations stop growing?

A

when they reach carrying capacity (K)

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6
Q

Maximum Sustainable Yield Model

A
  • in absence of overexploitation, population growth = highest at K/2
  • The MSY depends on r (rate of population growth) and K (carrying capacity)
  • these vary depending on characteristics of species concerned (reproductive rate etc)
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7
Q

What happens when fixed harvest (quotas) are set too high?

A

population driven to extinction

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8
Q

What happens when quota = MSY (Maximum Sustainable Yield Model)

A

harvesting will be sustainable if initial population level is above MSY, but lead to declines if population dips below MSY

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9
Q

Where are quota levels safer for harvesting?

A

low - only lead to decline if population goes below N1

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10
Q

What is required for a low harvesting quota?

A

accurate estimates of population size, K and r -> very challenging

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11
Q

What are proportional harvests?

A

dependent on population size
more sensible
all equilibria = stable, including MSY (which still occurs at K/2)
very difficult to implement as require constant, accurate population monitoring

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12
Q

Why are MSY modes oversimplistic?

A
  • r and K may vary e.g. depending on population age structure and environmental variation
  • more accurate models exist - hard to get accurate data to parameterise them
  • challenging to implement - especially when moving across boundaries
  • illegal harvesting and other sources of mortality must be taken into account
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13
Q

Types of overexploitation

A

Commercial
Subsistence
Recreational

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14
Q

What is commercial overexploitation?

A

unsustainable harvesting driven by a legal or illegal market
e.g. fishing - about 33% (possibly up to 66%) are overharvested

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15
Q

What can commercial overexploitation lead to?

A

huge population crashes and collapse of the industry
some populations are managed very well

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16
Q

What was the population crash of the Newfoundland Cod? (Commercial overexploitation)

A
  • population crashed by 99%
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17
Q

Why does overfishing not always lead to extinction? (Commercial overexploitation)

A

due to high reproductive rates of many marine fish, but population may not bounce back after harvesting stopped

18
Q

What can help fish sustainably? (Commercial overexploitation)

A

quotas but have problem
e.g. what about non-target species and excess catch?

19
Q

What percentage of harvest in fishing is put back into the sea? (Commercial overexploitation)

A

between 25% and 75% of harvest in fishing operations is dumped back into the sea (dead or dying)

20
Q

What solutions exist for fish harvest of non-target species and excess catch? (Commercial overexploitation)

A

e.g. improvement to fishing equipment
public awareness campaigns - help people choose their sources of seafood more wisely e.g. see the good fish guide

21
Q

What is whaling? (Commercial overexploitation)

A

Hunting of whales
1986 - International Whaling Commission (IWC) banned commercial whaling to allow stocks to recover

22
Q

What happens when larger species targeted, experiences a crash? (Commercial overexploitation)

A

then smaller species are targeted

23
Q

Example of species that have recovered well (Commercial overexploitation)

A
  • e.g. humpback whales reduced from >100,000 to around 10,000 - a 90% reduction -> populations now at >60,000 and increasing
24
Q

Example of a species that has recovered less well (Commercial overexploitation)

A
  • e.g. blue whale previous population: 200,000-300,000 current population around 2000-5000 whales despite being protected since 1966
25
Q

What is still low after population recovery? (Commercial overexploitation)

A

genetic diversity

26
Q

Effect on pinnipeds (Commercial overexploitation)

A
  • Many pinnipeds hunted to almost extinction in 18th and 19th centuries - fur and blubber
  • population sizes of many of these species recovered
  • Stoffel et al (2018) investigated current genetic diversity in 30 pinniped species
  • 11 species show genetic signs of severe bottlenecks, with effective population sizes declining to <500 - sometimes <50
27
Q

What species had a lower genetic diversity? (Commercial overexploitation)

A
  • went through bottlenecks
  • have small current population sizes
  • breed on land (easily accessible by human hunters)
  • Bottleneck size = not related to IUCN status, indicating population recovery in many cases (although 3 of 4 most bottlenecked species are currently endangered)
28
Q

What are the main solution for commercial overexploitation?

A

Certification schemes
- e.g. marine Stewardship council, Forestry Stewardship Council
- can’t boost standards across industry, but aren’t perfect
- rely on consumer awareness and buy-in

International agreements
- e.g. CITES - 36,000 species protected - 183 parties in CITES
Appendix I = trade permitted only in exceptional circumstances, 3% of all species (e.g. African rhinoceros, threatened with extinction)
Appendix II = trade strictly controlled, 97% of all species (e.g. Orchidaceae, at risk of becoming threatened)
Appendix III = request for assistance in controlling trade of species protected in species country (e.g. Chilean toad)

29
Q

Illegal shipments (Commercial overexploitation)

A
  • commonly run by organised crime syndicates
  • often seized at airports/ports
  • 76% of seizures are of CITES Appendix 1 or 2 species
30
Q

Trade networks (Commercial overexploitation)

A
  • complex
  • important progress made
  • current global resources allocated to combatting transnational wildlife crimes are in tens of millions of US $ globally = a fraction of resources available to those committing crimes
31
Q

What is subsistence overexploitation?

A
  • many people rely on wild plants, animals and fungi - food resource
  • 10,000 yrs ago, all food came from wild
  • Now: <1B people rely on wild plants, <1/th protein comes from wildlife in 62 developing countries, and almost 20% protein intake comes from wild fish for <3B people
32
Q

Why is some harvesting not sustainable? (Subsistence overexploitation)

A

due to increased human population sizes and advances in modern harvesting technologies

33
Q

Why are some location particularly vulnerable to subsistence hunting? (Subsistence overexploitation)

A
  • high human density
  • new road/transport links enable access
  • increasing commercial trade
  • difficult to regulate, considerations must be made to people who rely on subsistence hunting for food
34
Q

What is there a large threat of? (Subsistence overexploitation)

A

Zoonotic diseases

  • areas where both reservoirs of pathogens and human contact with wild meat = high
  • risks from major transport hubs
35
Q

How much of global human population participates in recreational fishing? (Recreational overexploitation)

A

around 11%

36
Q

What do recreational fishers target? And their effect? (Recreational overexploitation)

A
  • largest, most fecund individuals, which has disproportional effects on population growth
  • can lead to substantial population declines
37
Q

Effect of re-stocking programmes (for fish)? (Recreational overexploitation)

A
  • boost numbers
  • can damage natural populations e.g. by hybridisation of non-native species/populations, invasive species
38
Q

What is the impact of recreational fisheries in comparison to other threats? (Recreational overexploitation)

A

low impact

39
Q

Effect of unsustainable hunting practices from the colonial era? (Recreational overexploitation)

A

huge declines in many ‘big game’ species
- e.g. hunting and habitat loss reduced Bengal Tiger populations in India from 40,000 to less than 1,800 in 100 years

40
Q

What can harvesting at sustainable levels contribute to? (Recreational overexploitation)

A

local economy and retain cultural important traditions
can enable protection of land for conservation

41
Q

What is the argument against harvesting at sustainable levels? (Recreational overexploitation)

A

(especially for crueller hunting techniques)
- conflict with wildlife tourism
- much of money raised doesn’t stay in local communities
e.g. of the US$200 million generated annually from trophy hunting in Africa, only 3% reaches local communities

42
Q

Effect of management for specific target species and an example (Recreational overexploitation)

A

can damage ecosystems
e.g. grouse-shooting in UK
- around 8% of combined area in England and Scotland are managed for grouse-shooting
- regular burning to boost supply of young heather and remove trees and grass
- killing predators and mountain hares (some persecution is illegal)
- increases grouse numbers, at expense of many other (but not all) species

management could be worse - e.g. sika plantations and intensive grazing

management could be improved - restore ecosystem and support landowners and recreational hunters - need to get stake holders onboard

BIO234_Animal Conservation and Welfare (17 decks)

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