Transcript Local restoration efforts - Environmental Science & Policy

Restoration and Mitigation
Restoration Ecology
• Restoration ecology is the “science” of
returning degraded sites to something
approaching a natural state
• Ideally, it is not a substitute for conserving
natural areas but another means of
achieving the same goal
• The first goal is to maintain natural levels
of diversity and ecosystem functioning,
but restoration is necessary in the face of
wide spread habitat loss and degradation
Reasons for Restoration
• To restore heavily degraded sites including
modifying chemical/physical site parameters
to permit recovery
• To improve productivity and to prevent
further habitat loss, for instance reversing
erosion of sediments, decreasing turbidity
• To add conservation value to protected
habitats e.g. those invaded by exotic species
• To add conservation value to productive
areas e.g. restore areas being exploited like
oyster reefs
Mitigation
• Legislation now requires rehabilitation of
certain areas, e.g. creation of wetland
• Wetland (or other habitat) would be
created to “mitigate” or offset
(compensate for) losses elsewhere
• Mitigation is really restoration in where the
targeted habitat never existed
Mitigation
• Compensatory mitigation involves the
creation of a habitat of equal size/value in
trade for the loss/destruction of existing
habitat
• In most cases, mitigation requires creating
more habitat (2 to 1, 3 to 1) than what is
lost to development
• The problem is the certain destruction of a
vanishing habitat for the uncertain
promise of similar habitat, very
contentious issue
Problems with Mitigation
• Often the local flow regime or sediment
types are inappropriate for creating the
new habitat
• To create a new habitat, the existing
habitat, desirable or not, is destroyed
• Mitigation can proceed at a site some
distance from the damage
Wetlands Mitigation
• Wetlands mitigation is driven by a policy
of no net loss
• Wetlands are of course being lost due to
permit policies that allow wetlands
development of <10 acres without redress
• Historically the definition of a wetland has
been elusive
• Mitigation success has then been in the
eye of the beholder
• Generally, the loss rate has far outstripped
the successful mitigation rates
The Big Problems
• Recreating a wetland is extremely difficult
• Most attempts have been unsuccessful,
although there have been a few successes
• Criteria for defining success (even if we
know what a wetland is) are unclear
• Even if criteria are agreed upon, levels of
monitoring of mitigated sites are frequently
insufficient to assess success or failure
Other Problems
• Where do you put the mitigation project?
– Is it OK to provide new habitat at some
distance from the lost habitat?
– How far is too far away?
• Which habitat will be destroyed to create the
mitigated habitat?
– Which habitat is most expendable?
– Which species are extirpated?
Other Problems
• Where do you get the species to
repopulate the mitigated area?
– Do you tear asunder another habitat?
– What if it involves rare or threatened
species?
• Where do you get the substrate for the
project?
– Is it OK to strip sands or other substrate
from another area?
– If plant habitats (salt marsh), are
seedbank intact?
The Most Pressing Problems
• What is the basis for comparison
between the mitigated site and control
or reference sites?
• How are reference sites chosen?
• How does this take place?
• Who decides?
Goals and Concerns for
Restoration
• Identify the processes contributing to
habitat degradation
• Determine criteria for evaluating success,
usually comparing with a reference site(s)
• Develop methodology to meeting those
criteria
• Incorporate methodology into strategies
for management and planning
• Monitor and evaluate the success with
respect to a reference site(s)
Comparisons with
Reference Sites
• Species diversity
– Is the assemblage as diverse as the reference?
• Productivity
– Are levels of net productivity equal (including
photosynthesis, respiration, herbivory)
• Nutrient retention
– Is the restored system losing nutrients at the
same rate?
• Biotic interactions
– Are key species functioning the same way?
• Invasibility
– Is the restored system equally invaded by
exotic species?
Successes and Failures
• Habitats have been quite variable in how
successful they have been restored
• Salt marshes, and a few other habitats
with limited species diversity or structural
simplicity have seen some successes (not
universal)
• It is clear from our few successes how
poorly we understand the nature and
structure of natural systems
Restoration as Succession
• The basis of restoration is to facilitate a
natural successional process
• In many cases, the successional process is
accelerated or shortened to reach the
desired stage
• In other cases, succession is intentionally
interrupted to maintain a certain
successional stage
• Often the restoration process is shooting at a
moving target
Restoration as Succession
• Restoration of severely damaged areas may
need to proceed in two steps
• First is to ameliorate the site conditions
• In wetlands for example, this is could be
accomplished by removing levees or grading
sediments to ensure proper tidal exposure
• Second is to remove exotic community (if
present) and re-establish the native
community (if required)
Marsh Restoration
Some Lessons from
Succession
• The final assemblage may be dependent
on the order in which species enter into a
system
• Priority effects have been demonstrated in
a number of systems in which the final
assemblage differs depending on the
order in which species are established
• It may also be the relative abundances as
well as the timing of their establishment
that may determine this outcome
Some Lessons from
Succession
• Generally, even the most disturbed site
will have some remnants (known as
residuals) remaining
• In salt marshes this could be a seed bank
in the sediments
• For coral reefs, this could be nearby
corals to provide recruits
• Also, abiotic characteristics, soil nutrients
and conditions may remain intact as well
• Heavily degraded sites may have less of
these characteristics
Salt Marsh Restoration
Agua Hedionda, SD County
Agua Hedionda Lagoon
• A southern California company got a
permit to fill part of the Agua Hedionda
Lagoon
• Three tidal basins (1 ha.) were required
to mitigate this loss
• An adjacent upland area was graded to
create three basins with tidal access
• Pickleweed (Salicornia) was planted
and irrigation provided
Agua Hedionda Lagoon
• Vegetation failed in all three basins
• No quantitative evaluation of the
project has been carried out
• What remains is bare sediment with
salt crust rather than the vegetation
promised earlier
• Reference sites were ambiguous and
not compared
Agua Hedionda Lagoon
• In hindsight, excavation was not deep
enough
• Soil texture was not fine enough
• No follow up was required beyond the
period required for pickleweed
irrigation
• No long-term monitoring was carried
out
Batiquitos Lagoon
• This was an off-site or “out-of-kind”
mitigation project that intended to trade
quality for quantity in trade for LA filling part
of San Pedro Bay
• It currently was a non-tidal wetland provides
nesting habitat for the endangered California
Least Tern and threatened Snowy Plover
• It is slowly filling in and drying out (as many
west coast estuaries do)
Batiquitos Lagoon
• Changing it from a non-tidal to a tidal
wetland has unknown ramifications
• It will increase habitat for invertebrates and
fishes and allowances are being made in the
enhancement plan
• It isn’t clear whether (and when) this lagoon
would lose it’s wetland function if left alone
• It’s also not clear which functions will be
changed once flushing commences
Coral Reef Restoration
• The approach here is to increase the
recruitment of corals in this habitat
• Minimize overgrowth of algae
• Minimize grazing by corallivorous fish
• Rely on recruitment from other sites
Coral Reef Restoration
Coral Reef Restoration
Coral Reef Restoration
Outplant coral heads
Outplant boulders for recruitment
Oyster Restoration
• Oyster restoration is a rapidly increasing
activity on both east and west coasts of
the US
• Oysters are both an important fishery but
also provide habitat for fish and inverts
• They can also have a positive influence on
water quality
Restoring habitat and ecosystem services in estuaries
• Ecosystem services lost and
consequences
• History of oyster exploitation
• East coast restoration methods
• Introduction of non-native oysters
• Recovery of ecosystem services is
landscape-dependent
• Local restoration efforts
Overfishing has resulted in oyster fishery collapse throughout Eastern
estuaries
Newell, 1988
Filtration of the water column in estuaries takes a heck of a lot longer!
What ecological goods &
services do oysters provide?
Filter Water
Stabilize Adjacent
Habitats
Produce
Valuable Fish
Collapse = Loss of Goods and Services
Year
History of oyster reef exploitation: a guide
for restoration efforts
2000
1950
1900
1850
1800
1750
1700
1650
Earliest
importation
Peak in oyster landings
Earliest law
Ditance from Wellfleet, MA (km)
Earliest dates of
reef degradation
indicate how long
each estuary has
been exposed to
destructive fishing
practices
Kirby 2004
New York - 1808
1830
1829
1884
North Carolina - 1902
1908
Estuaries at the end of the sequence
may be easier to restore
Oyster restoration methods
Oyster reefs (~8 ft tall)
created from oyster
shells--sometimes
limestone, concrete, or
fossil oyster shells
Oyster recycling
Oyster restoration methods
Shell being off-loaded from a
barge at a Rappahannock River
(VA) reef restoration site. Note
the tops of the 8 foot+ reefs
exposed at low tide.
Oyster reef restoration may use heavy equipment….
….or lots of volunteers
Oyster restoration methods
Chesapeake Bay
Foundation oyster
gardening project
How is it done?
1. Each participant builds a set of four 'oyster cages', made from wire
mesh, which will hang from the dock for growing oysters. The
gardener also receives about 2,000 seed oysters.
2. Gardeners grow their oysters for about a year until they are
around two inches in length.
3. Oysters are collected and planted on a rebuilt reef in local waters.
4. The gardener starts over with a new batch of seed.
Oyster restoration results
Before
After
Not so good oyster restoration results
Despite these efforts,
numbers still at all
time low, not just
overfishing--disease
is also taking its toll.
Diseased oyster
“Dermo” or “MSX”
Normal oyster
Local restoration efforts
Pacific oyster (Crassostrea gigas) from Japan
• extensively farmed in Pacific NW
• locally in Tomales Bay
•dwarfs our native
•2-3 x bigger than Eastern oyster
Olympia oyster (Ostreola conchaphila)
• our only native oyster
• range Sitka, Alaska to Baja
• max size is 6-7 cm
History of Olympia oysters
• Native (Olympia) oysters were an important food for the Ohlone people for
thousands of years (IKEA in Emeryville on top of massive shell midden)
• In the late 1800’s, thousands of acres of Olympia oysters were cultivated on SF
Bay tidal flats--hugely successful fishery (pricey--costly to shuck all those little
oysters)
 by 1900, essentially gone--overharvested
• Other species (first eastern, then Pacific) brought in and cultivated
• By 1917 all oyster production in SF Bay ended--heavy sedimentation
(especially from hydraulic mining), dredging, filling, domestic and industrial
pollution, influx of invasive flora and fauna
 Only small relict populations of native oysters in the bay today
In last 3 years--new efforts to assess restoration potential for native
oysters in SF Bay
Why? Not for fishery--water quality still not good enough
--restoration for its own sake
--habitat value of oyster reefs (tiny but create reefs 10’s of feet high)
--water quality benefits
Local restoration efforts
In San Francisco Bay: beginning in 2002, dead C. gigas shell
put out in locations throughout the bay to see if native oysters would
settle given suitable substrate……….Answer = yes!
Local restoration efforts
More ambitious project to actually restore small populations at three
locations in Tomales Bay
• Placed oyster shell in bags stacked in pyramid shape on pallets
• Monitoring recruitment of native oyster to the shell substrate
• Oysters have been slow so substrate isn’t the only answer