Transcript Chase Mahoney

Prospects for Biodiversity
Author: Martin Jenkins
Summary: Chase Mahoney
Critique: Asa Angeles
Introduction
 9,000,000,000 people
 Imagine their impact.
 “What will be the state of the world’s
biodiversity in 2050?”
 Prospects for Biodiversity offers an answer
to this question.
Overview
 Assumptions for extrapolation
 Human influences and their impacts
– Terrestrial Ecosystems
– Aquatic Ecosystems
 Do these impacts matter?
Assumptions for Extrapolation
 United Nations global population estimation
– 9 Billion (2050)
– 6-7 Billion (2003)
 The human race will conduct its affairs in much the
same manner as today.
 Intergovernmental Panel on Climate Change
Scenarios
– 1oC to 2oC increase in average surface temperature.
– 100 to 200 ppm increase in CO2 concentration.
Major Human Influences on
Land
 Habitat conversion
– Clearing land for farming
 Intensification
 At least 120 ha by 2030
 By 2050 much more
 South America and sub-Sahara Africa
– Most biologically diverse regions in the world.
– Disproportionate loss in biodiversity
Major Human Influences on
Land
 Habitat conversion
– Clearing land for farming
 Dense tropical forest -> Fragmented/Degraded
 Resemble temperate forests of North America
 350 species of avifauna (3.5%) will become extinct.
 Surviving species live in heavily protected managed
areas.
Major Human Influences on
Aquatic Ecosystems
 Habitat Conversion
– Destruction by siltation
 Land runoff
 Coastal development
– Pollution
– Large-scale Hydroengineering
Major Human Influences on
Aquatic Ecosystems
 Habitat Conversion
– Fresh water biodiversity
has suffered the
heaviest losses over
the last 30 years.
– These losses are
expected to continue
– Coral Reef destruction
Major Human Influences on
Aquatic Ecosystems
 Exploitation of wild resources
– Direct exploitation through fishing
 Current rates lead to extinction
 Large species and top marine predators scarce or
extinct.
Does it Matter?
 Ecologists and Conservationists struggle to
demonstrate benefits of diverse intact
systems.
Diverse species-rich systems
Intensively managed systems of nonnative
species (farms)
Does it Matter?

Benefits are marginal and local
– Few cases have shown benefits of natural
systems

Forest destruction
– Infertile unusable land has obvious impacts on
human existence.
– Replacement shows no negative impacts.
Does it Matter?
 Experts agree most large terrestrial species
are extinct as result of human influence.
– 40,000 to 50,000 years
– Systems we consider natural aren’t so.
– Don’t show catastrophic consequences.
Does it Matter?
 Real life example
– 38 species of avifauna existed in New Zealand.
– 9 exist today
 Most of which are endangered
– Huge loss of biodiversity
 No signs of suffering from a crisis.
– On what grounds can we base our belief that
similar losses will result in crisis in other areas.
Does it Matter?
 Still may not abuse the biosphere
indefinitely.
– Unforeseen threshold
– Catastrophic consequences
 More likely cause of catastrophic
consequences will be abrupt climate shifts.
– May begin with manipulation and abuse of the
biosphere.
Conclusion
 Jenkins scenario assumptions
– Climate
– Population
– Similar method of conduct
 Human actions have direct influences on
surrounding ecosystems.
 Losses in biodiversity do not have immediate
negative impacts on human existence.
– Still be aware our impact may eventually trigger other
catastrophic events.
Prospects for Biodiversity
By Martin Jenkins
Summary: Chase Mahoney
Critique: Asa S. Angeles
Critique Outline
 Positive Critique
– Citations
– Good Points
 Constructive Criticism
 Questions
Positive Critique
 Evidence
– 24 citations, including links to web sources
Year of Publication of Citing Articles
6
5
4
3
2
1
0
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
Living Planet Index
282 species
195 species
217 species
Other Good Aspects of the Article
 Honest tone; mostly not over-dramatized
– Says estimating extinction rates is difficult
– Admits that scientists struggle to show human
benefits from “intact” wild systems
– New Zealand went from 38 to 9 species of birds
in a few centuries, but does not suffer
 The future will probably be this way
Constructive Criticism
 Minor: Of the 24 citations, 7 are Science articles
 How much does it matter?
– Says “natural” systems that really aren’t natural still
function (recall New Zealand)
– But somewhat dramatizes at the end: “…some threshold
may be crossed, with unforeseeable but probably
catastrophic consequences for humans.”
– Then he immediately takes back this claim: “It seems
more likely that these consequences would be brought
about by other factors.”
– So…How much does it matter?!
Questions?