Transcript rivercenter.uga.edu

DOMINANT AND EMERGING PARADIGMS IN
CONSERVATION ECOLOGY
The meaning of "paradigm" as a scientific
"world view"
How and why paradigms change
Dominant paradigms of
previous decades
An old and enduring
question: "What controls
population dynamics?"
1. Population dynamics
driven by the environment,
especially weather
• Thrips, roses, weather
• Popular in Europe and Australia
• Emphasizes stochastic (chance) over
deterministic, not directly densitydependent
• Useful in degree-day models for
biological control
Thrip damage on roses
Severe winters increase
mortality of deer but
increase survival of
grizzly bear and wolf
young
thrips
2.
Population dynamics driven by
competition
• Common idea in New World
• Influence of Darwin and Hutchinson
• Fundamental vs realized niche gave rise to
idea of community matrix and field tests
• Deterministic generally but stochastic
processes can be important
African grazing animals:
Competition can have
strong temporal component
Plants frequently
compete for nitrogen in
temperate zone and
phosphorus in tropics
3.
Population dynamics driven by
predator x prey
• Wildlife management
• Early interest from presumed conflict
with human hunters; livestock death
• Ideas: search-handling, prey dispersal,
predator satiation, prey refugia
• Keystone predator, competition,
diversity
• Deterministic and stochastic
Starfish as keystone
predators may reduce
competition from
mussels and enhance
biodiversity.
Crown of thorns starfish
may reach large numbers
and reduce coral
biodiversity.
Genetics and behavior
Refugia for prey
Large area required
Predators can be prey
The other old and enduring question, "Why
are there so many species?"
Evolutionary
Versus
Ecological time
Biodiversity in evolutionary
time
• Biogeography (ancient legacies)
• Stable environments facilitate narrow
niches, hence more species packing
(rainforests and deep ocean??)
• Speciation following dispersal barriers
• Speciation following major extinctions
Biodiversity cycles
over geological time.
Rainforest diversity ??
Deep
ocean
vents
have rich
diversity
Biodiversity in ecological time
• Environments that are both highly
productive and heterogeneous have
high biodiversity (not always)
• Stable competitive environments should
have fewer species due to displacement
(note contrast with speciation)
• Highly variable environments dominated
by colonizing species, diversity low
Emerging Paradigms
• New emphasis on spatial and temporal
scale-dependent processes
• Coupling population dynamics with
ecosystem analyses
Metapopulation of mountain lions in So
California. Some are sinks (e.g.,Laguna)
• Stability at the large scale is dependent
on non-stability processes acting at
smaller scales
• Coupling bottom-up with top-down
processes (forest example)
• Communities are comprised of a mix of
weakly and strongly interacting species
(esp. protect keystone
species/resources)
• Stability at the large scale is dependent
on non-stability processes acting at
smaller scales (forest example)
• Coupling bottom-up with top-down
processes (forest example)
• Communities are comprised of a mix of
weakly and strongly interacting species
(esp. protect keystone
species/resources; sometimes conflicts
with people, sometimes stewardship)
Forest canopy looks homogeneous and stable at this
scale
Spatial heterogeneity is evident
from digitized image (left) and
very evident from enhanced
spectral imagery (below)
At a smaller scale you
may pick out particular
causes of spatial
heterogeneity. Pine bark
beetles kill trees (left)
which eventually result in
forest patches of different
ages (below)
At the smallest scale critically important processes of
nutrient uptake take place that influence productivity
and additional spatial heterogeneity.
To understand forest structure and change you need to
understand top-down processes (disease, fire, beetles) and
bottom-up processes (nutrient uptake). Spatial and temporal
scales are very different.
• Ecosystems are open so landscape
scale is important (from small ponds to
“dead zones”
• Ecosystems have characteristic
disturbance regimes (complicated by
changing environment)
• Rare episodic events can leave legacy
(Mt St Helen eruption)
• Legacies generally important (pig and
cattle drive example)
Intermediate Disturbance
Hypothesis originated with
Connell’s observation of
tree falls in Australian
rainforests.
Frequency distribution of
gaps created by tree falls
gave rise to the
Intermediate Disturbance
Hypothesis…important in
forest management
Boulders of different sizes
(=different stability) used to
test Intermediate Disturbance
Hypothesis
Disturbance patches may be small, as in this leafcutter ant colony.
Or very large. This is Mt. Saint Helens, 1970, pre-eruption
Mt. Saint Helens after the 1980 eruption
Disturbances have a natural history and a legacy of effects.
Time of eruption in spring was important. Many small
animals survived in pocket gopher burrows. Seeds of many
plants were stored in marmot burrows.
Hurricane Dean Monday afternoon…heading towards the
Sian Kaan reserve as a category 5 storm. Dean’s path
over the ocean leaves cool and nutrient-rich waters.
H. Dean cat. 4 skirts the south coast of Jamaica
H. Dean and house destruction in Kingston, Jamaica
Sian Kaan Biosphere
Reserve. About 30
miles north of the
eyewall of H Dean.
This is the zone of
greatest wind and
ocean surge forces.
Indigenous maya living in the
Sian Kaan Biosphere Reserve
harvest conch and spiny lobster
on a sustainable schedule.
Spiny lobster
Why H Dean did little damage to Sian
Kaan….mangroves absorb the storm energy
Typical dense stand of mangroves along estuary
Mangroves protecting the Sian Kaan lagoon
where conch and lobster are harvested. The
mangroves provide a critical “environmental
service”…a rapidly emerging paradigm or focus
in conservation biology.
Mangroves destroyed to
make a shrimp pond. An
economically and
environmentally important
ecosystem (environmental
service) is replaced by a
short-term economic
activity.
Shrimp ponds in
mangroves are often druglaundering operations.
Shrimp ponds can be sustainably operated in
mangrove regions if they are located on mudflats.
Finding the appropriate economic and
environmental value of ecosystems as
environmental services is a major
focus of conservation.
•
•
•
•
Watersheds
Riparian forests
Salt marshes
Many other examples
Ecosystem Services
People are both players and stakeholders in
conservation initiatives and ecosystem processes in
general. Recognizing and measuring “Ecosystem
Services” (natural and economic value of the
environment) is an increasingly important goal for
conservation ecologists.
Decline of pollinators represents loss of a major
environmental service.
Why are pollinators declining so
rapidly??? 36% of honeybee hives
lost 2007. Native bee decline??
Disease (several exotic)
Chemicals to control varroa mites make
honeybees susceptible to disease
Pollutants
Future…Climate change uncouples flower
phenology from bee emergence.
Many scientists now believe that
disease is an important component in
shaping populations and communities
Domestic cats are hosts for
toxoplasmosis. Lethal to sea otters
and of increasing concern for
humans (zoonotic).
Avian malaria
especially serious
for island
populations that lack
resistance. Mosquito
vector feeding on
Hawaiian
Honeycreeper.
But like other themes in
conservation, disease is also
investigated in a larger
environmental context.
Mystery of lion
population crashes
African buffalo are not usually
bothered by tick fever.
When stressed by drought
the buffalo become heavily
tick infested and weakened
by tick fever.
When lions feed on
weakened buffalo they get
tick fever, usually not fatal.
Lions weakened by tick fever are highly susceptible to
canine distemper.
Canine distemper virus
Rhodesian lion dog
Drought weakens buffalo making them susceptible to
tick fever. Lions get tick fever by eating sick buffalo.
Weakened lions die from canine distemper.
So….agricultural demand for water coupled with
climate change create more frequent droughts.
More farmers mean more farm dogs and higher risk
of canine distemper transfer to lions.
Population crashes of lions results from this complex
interaction.
But don’t conservationists
mainly focus on endangered
species?
• Many do but their approaches are changing
to include larger scales.
• Some examples
-riparian plants and ice scour
-grizzly bears and whitebark pine rust
-Dickcissel bird and Colombia rice pests
-darters and parking lots
Paradigm-summary
• Old paradigm, “What controls
population dynamics?”
• A) Environment-stochastic
• B) Competition-deterministic
• C) Predators-significance of refugia,
affect competition, keystone species
Summary
• The other enduring paradigm, “Why are there so
many species?”
• A) Evolutionary time, biogeography, extinctionspeciation cycles, stable environments (species
packing)
• B) Ecological time, high productivity plus spatial
heterogeneity, highly stable and highly variable
environments often have fewer species.
Summary
• Emerging paradigms focus on nonequilibrium processes, especially
disturbance regimes
• Conservation management emphasizes
maintaining appropriate disturbance
regimes
• Disturbances have important natural
histories and legacy effects
Summary
• Resiliency to disturbance and concern
over environmental degradation led to
idea of ecosystems providing
environmental services
Summary
• Important emphasis on processes that
are coupled and occurring at different
spatial and temporal scales
(metapopulation structure and forest
examples, ecology of disease, dead
zones, etc etc)