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 boulders for recruitment

Outplant coral heads

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

• Ecosystem services lost and consequences

• History of oyster exploitation• East coast restoration methods

Restoring habitat and ecosystem services in estuaries

• 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, 1988Filtration of the water column in estuaries takes a heck of a lot longer!

What ecological goods & services do oysters provide?

Filter WaterProduce

Valuable FishStabilize Adjacent

Habitats

Collapse = Loss of Goods and Services

New York - 180818301829

1884

North Carolina - 1902

1908

Earliest dates of reef degradationindicate how long each estuary has been exposed to destructive fishing practices

History of oyster reef exploitation: a guidefor restoration efforts

Earliest law

Peak in oyster landingsEarliest

importation20001950190018501800175017001650

Yea

r

Ditance from Wellfleet, MA (km)

Estuaries at the end of the sequence may be easier to restoreKirby 2004

Oyster reefs (~8 ft tall) created from oyster shells--sometimes limestone, concrete, or fossil oyster shells

Oyster restoration methods

Oyster recycling

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 restoration methods

Oyster reef restoration may use heavy equipment….

….or lots of volunteers

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.

Chesapeake Bay Foundation oyster gardening project

Oyster restoration methods

Oyster restoration results

AfterBefore

Diseased oyster“Dermo” or “MSX”

Normal oyster

Despite these efforts, numbers still at all time low, not just overfishing--disease is also taking its toll.

Not so good oyster restoration results

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

Local restoration efforts

• 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

History of Olympia oysters

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

In last 3 years--new efforts to assess restoration potential for native oysters in SF Bay

In San Francisco Bay: beginning in 2002, dead C. gigas shellput 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

Local restoration efforts