ENVI 30 Environmental Issues - University of San Diego

I.
Biodiversity
–

Factors


E.
Exotic Species

•
Species invasions may profoundly affect
ecosystems

•
Detrimental exotic species usually are

•
Superior competitors

•
Ex

–

Argentine ants, starlings, zebra mussels

•
Effective predators

•
Ex

–

Nile perch, mongeese


I.
Biodiversity
–

Factors


E.
Exotic Species

1.
Zebra mussel

•
Competitor in Great Lakes and elsewhere

•
Transported from Europe in ballast water

•
Fouling organism

•
Restricts movement of water through intake
pipes

•
Colonizes boat hulls, pier pilings, buoys, etc.

•
Fouls other organisms (clams, mussels)

•
Filter feeder
–

removes larvae and particulate
material

•
Outcompetes native shellfish species for food
and space

•
Removes larvae from water

I.
Biodiversity
–

Factors


E.
Exotic Species

2.
Mongoose

•
Predator in Hawaii

•
Introduced in 1883 to combat rat population

•
Prey on native birds

3.
Lionfish

•
Venomous predator

•
Introduced in Caribbean/W Atlantic
ca.

early/mid
1990’s

•
Preys on 65+ spp. of fishes

•
No natural predators


Nile perch
–

Lake Victoria

Brown tree snake
-

Guam

Argentine ants
-

California

Caulerpa taxifolia

-

California

II.
Biodiversity
–

Value


A.
Value to Humans

•
Economic

•
Ex

–

Lomborg: $3
-
33 trillion annually

•
Biodiversity loss could lead to
removal of species

that benefit
humans but aren’t currently known to do so

•
Ex

–

Chapin et al. suggested increase in frequency of
Lyme disease

during 20
th

century may have been related to increase in abundance of
tick
-
bearing mice (once controlled by food competition with passenger
pigeons)

•
Species extinction
reduces potential pool

of species containing
chemical compounds with pharmaceutical or industrial
applications

•
Counter

–

Many pharmaceutical companies now use
directed design

to
search for new drugs

•
Problem

–

Benefits may not be obvious

•
Difficult to convince people that it’s important to preserve something
with no immediately apparent intrinsic value to them (
charisma?
)

•
Ex

–

Economic value of viral resistance added to commercial strains of
perennial corn through hybridization with teosinte (Mexican wild grass)
is ~ $230
-
300 million

•
Ex

–

Weedy tomatoes from Peru

•
Discovered in 1962 during search for potatoes

•
Seeds sent to researcher at UC Davis who used plants to breed with
other tomatoes

•
In 1980 after nearly 10 generations of crossing and backcrossing, new
strains were produced with larger fruit, improved pigmentation and
increased concentrations of sugars and soluble solids

II.
Biodiversity
–

Value


B.
Ecosystem Value

•
Biodiversity can have large effects on ecosystem
stability and productivity

1.
Benefits of biodiversity

a.
Productivity

•
Halving species richness reduces productivity by
10
-
20% (Tilman)

•
Average plot with one plant species is less than half
as productive as a plot with 24
-
32 species

•
Question

–

Can these results be extrapolated to
other systems and time/space scales?

b.
Nutrient retention

•
Loss of nutrients through leaching is reduced when
diversity is high

•
Caveat

–

Studies to date have focused on low
diversity communities (
Why?
); can those results be
generalized?

II.
Biodiversity
–

Value


B.
Ecosystem Value

1.
Benefits of biodiversity

c.
Ecosystem stability

•
Mechanism

•
Multiple species within a trophic level compete for
resources

•
If abundance of one species declines due to perturbation,
competing species may increase in abundance

•
Individual species abundances may vary, but community
as a whole is more stable with more species

•
Consequences

•
High diversity doesn’t guarantee that individual
populations won’t fluctuate

•
Ex

–

Higher diversity (unfertilized) plots of native plant
species maintained more biomass during drought than
lower diversity (fertilized) plots

•
High diversity may confer greater resistance to pests and
diseases

•
Ex

–

Higher diversity plots of native plant species had
greater resistance to fungal diseases, reduced predation
by herbivorous insects and reduced invasion by weeds

II.
Biodiversity
–

Value


B.
Ecosystem Value

2.
Considerations

a.
Species richness vs. Species evenness

•
Simple species richness may be deceptive as an indicator of
biodiversity and ecosystem stability

•
Evenness usually responds more rapidly to perturbation
than richness and may have important ecosystem
consequences

•
Richness is typical focus of studies and policy decisions

b.
Importance of individual species

•
Charismatic megafauna:
What about non
-
charismatic species?

•
Different species affect ecosystems in different ways (keystone
species
vs.

non
-
keystone species)

•
Ex

–

Sea otters/Sea urchins/Kelp forests in eastern Pacific
Ocean

•
Question:

How many species are required to maintain “normal”
ecosystem function and stability?

•
No magic number

•
Losing one ant species in a tropical forest may have less
immediate impact than losing one species of fungus that
is crucial to nutrient cycling in the soil

III.
Biodiversity
–

Management


•
Strategies outlined in Convention on Biological
Diversity

•
Developed between 1988 and 1992

•
Opened for ratification at UN Conference on
Environment and Development (Rio “Earth Summit”)

•
Ratified by 168 nations; went into force in Dec 1992

•
Objectives
–

“…the conservation of biological
diversity, the sustainable use of its components and
the fair and equitable sharing of the benefits arising
out of the utilization of genetic resources…”

•
Articles 8
-
9 specify a combination of
in situ

and
ex situ

conservation measures

•
Primary use of
in situ

conservation

•
Use of
ex situ

measures as a complement

IV.
Genetic Engineering


A.
Background

•
Concept based on idea that organisms share
same basic genetic material (DNA)

•
Functionally similar units (genes)

•
Same basic mechanisms of
gene expression

•
Theoretically possible to transfer genes
between organisms and expect traits to be
transferred faithfully

•
Insertion of a foreign gene into a species’
genome creates a
transgenic

organism

•
Inserted gene may or may not be expressed

•
Theoretically, no limits on what can be inserted

•
Ex

–

Insulin gene inserted into bacteria

•
Ex

–

UCSD researchers inserted bacterial
luciferin/luciferase genes into tobacco plant

•
Technology offers potential to create novel
organisms with unusual and potentially
beneficial attributes

IV.
Genetic Engineering


A.
Background

•
Concept based on idea that organisms share
same basic genetic material (DNA)

•
Functionally similar units (genes)

•
Same basic mechanisms of
gene expression

•
Theoretically possible to transfer genes
between organisms and expect traits to be
transferred faithfully

•
Insertion of a foreign gene into a species’
genome creates a
transgenic

organism

•
Inserted gene may or may not be expressed

•
Theoretically, no limits on what can be inserted

•
Ex
–

Insulin gene inserted into bacteria

•
Ex
–

UCSD researchers inserted bacterial
luciferin/luciferase genes into tobacco plant

•
Technology offers potential to create novel
organisms with unusual and potentially
beneficial attributes

IV.
Genetic Engineering


B.
Purposes

1.
Accelerate and refine selection process

•
“Normal” hybridizing limited by

•
Generation time

•
Combining entire genomes, not just traits of interest

2.
Create otherwise unattainable hybrids

•
Ex

–

Arctic flounder and strawberry or tomato

•
Bottom line

-

Genetic engineering of organisms is
intended to benefit humans, not modified organisms

•
Proponents stress
potential benefits

to
humankind and the environment

•
Opponents emphasize
potential risks

and
concerns

•
Conversation with Hugh Grant