| Biology
141
Lewis & Clark College |
|
K.E. Clifton |
More on the ecology of reserves
The role of ecology in the design of reserves:
Some basic concepts: SLOSS - Single Large Or Several Small?
Cores and buffer zones
Nodes and corridors
What are the "needs" associated with establishing a reserve or protected area?
Three things
Representation
Replication
Connectivity
Do reserves work?
Greater diversity and abundance inside?
Yes! Especially those BOFFFS... coined for marine reserves, but true for any reserve
"Spillover"
Yes!
New Zealand Marine Reserve system, Great Barrier Marine Park Authority, Monterey Bay National Marine Sanctuary
So, why don't we have reserves all over the place?
The theory vs reality - the challenges of implementing a reserve
Two examples:
Maziwe reef - Tanzania
Oregon coast - Watch Common Ground III on the establishment of Marine Reserves in Oregon
Ultimately, you need ecological knowlege to understand how to design and manage a reserve
The resources being protected be clearly defined and understood.
Think of the importance of basic biology (food/sex/death)
Species area curves
Population growth and recovery models
What else is neccessary for success:
Community involvement vs exclusion
Restoration ecology: in principle vs in reality. Why is there a problem in the first place... has it been fixed?
Science vs popular attitudes about certain species.
Consider the Marine Mammal protection act
The idea of "sustainable harvest
Sustainable resourse use involves the regulated consumption of renewing resources such that depletion (consumption) matches renewal.
In theory, sustainable resource use should allow long-term exploitation
Management strategies are geared towards maximizing harvest: an issue of economics
An example of managed take: Fisheries practices.
Fisheries:
Fish are an important source of animal protein and rates of harvest have increased steadily over the last 50 yrs.
This could be a good thing: Carbon footprints for ectothermic sources of animal protein are smaller
"Fishery yields" (the number of fish harvested in an area) are strongly linked to local primary productivity.
90% of the worlds fish come from nearshore (or "inshore" waters).... why?
What does this mean with regard to feeding the human population?
Fisheries occur on all scales, from reef-to-reef practices to global fishing fleets.
As technology has improved, more energy is expended to travel farther and catch more fish.
Modeling fisheries ("take" from populations).
Presumes that population growth follows classic logistic expectations.
This implies density dependence
The fastest rate of population growth defines the "Maximum Sustainable Yield" (MSY).
Thus, if you can catch fish at a rate that is lower than the population growth rate, the fishery should be sustainable (in theory).
Possible reasons why this simple model may not be appropriate.
Collecting data on population dynamics
Life history considerations
"Opportunist" vs "Competitor"
Spatial and temporal patterns of occurence obscure estimates of population size and can alter rates of effort and harvest.
On top of all this: the tragedy of the commons
The oceans belong to no one (or everyone)... so take is not regulated beyond 200 mile international boundaries
Who wins between "altruists" and "exploiters" under such conditions?
Finally, economic factors may make catching almost all the fish a profitable venture.
Bluefin tuna economics
The fallacy that fisheries are static: harvesting as "natural selection" and evolution in body size and life history.
"Prey switching" can theoretically release target species from over exploitation, but the switch often comes only when the prey become very rare.
Other consequences of over fishing:
reduction in trophic position of targeted fish
ecosystem change from food-web alterations
Solutions to fishery problems:
Limit take:
No take zones: source vs sink thinking
Regulate size or age of harvested species
Farming (Aquaculture).
