Transcript BCB341_Chapter12_restoration

RESTORATION ECOLOGY
INTRODUCTION TO RESTORATION
 Many areas are partly destroyed or degraded through human
action.
 This need not be a permanent state of affairs
 Restoration is possible on a local basis provided materials
(reservoir of local species) and expertise are present
 Provides an opportunity to put research findings into practise
 Great potential for enlarging and
connecting conservation areas
 May be a misuse of resources –
pros and cons of restoration must
be added carefully
 The active corollary to
conservation biology – rather than
protecting areas that are under
threat, it attempts to increase the
extent of “natural” areas
TERMS
 Ecological restoration – the practice of restoration.
 “The process of intentionally altering a site to establish a defined,
indigenous, historic ecosystem. The goal of this process is to
emulate the structure, function, diversity and dynamics of the
specified ecosystem” (society of Ecological Restoration, 1991)
 Restoration ecology – the science of restoration (refers to
research and study of restored populations, communities &
ecosystems.
 Mitigation process (offsets) – where a new site (often
incorporating wetland areas) is created or rehabilitated as a
substitute for another area which is destroyed or undergoing
development.
 Reference sites - areas with a comparable species composition
and ecosystem structure that are used to determine appropriate
introductions and processes for a restoration site.
WHY RESTORE?
 Disturbance and damage to an ecosystem can be a
natural process (eg: lightning-triggered fires)
 In this case, recovery to a stable climax community
raises the biological diversity briefly and undergoes a
process of succession
 Some systems may be so damaged that they are
unable to recover by themselves:
 Mine sites/dumps – high erosion rate, potential soil
toxicity, low nutrient status
 Areas where degrading agent is still present cannot
undergo restoration (eg: overgrazed areas)
 Where original species assemblage has been extensively
eliminated with no source of colonists
INCENTIVES FOR RESTORATION
 Material benefits:
 Economy depends on balance between developed & natural
areas (ecosystem service)
 (eg) costs money to clean polluted water, but natural sources
provide it free
 If development impinges on ecosystem function too heavily, the
economy & quality of human life deteriorates
 Existential reasons:
 Improves personal relationships with nature (especially when
conducted at a community level)
 Empowers people and stimulates stewardship
 Heuristic reasons:
 Allows the study of ecosystem services through reassembly
 Trial & error through hypothesis construction & testing
(restoration ecology)
APPROACHES TO RESTORATION1
 No action
 Too expensive
 Previous attempts have failed
 System may be able to recover on its own (eg: agricultural fields
returning to the wild)
 Rehabilitation
 Replace degraded ecosystem with another, using simple species
assemblage (eg: turn degraded forest into productive pasture)
 Establishes a functioning community on site & restores ecosystem
services
 Partial restoration
 Restore some ecosystem functions & some original species
 Start with hardy local species, leaving rare species for later efforts
 Complete restoration
 Restore complete original species composition, structure & function
through a comprehensive reintroduction process
APPROACHES TO RESTORATION2
Ecosystem
function
Replacement using a
few species
(rehabilitation)
Replacement using
many species
(rehabilitation)
ORIGINAL
ECOSYSTEM
Biomass, nutrient content, etc.
Complete restoration to original
Partial restoration
No action; ecosystem recovers on its
own via succession
DEGRADED ECOSYSTEM
No action; continued deterioration
Ecosystem
structure
Number of species & ecosystem complexity
CASE STUDY: THE HEATH
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FRITILLARY
 Mellicta athalia has declined rapidly in England
since 1950.
 Relies on woodland habitats
 Larvae eat common cow wheat, Melanpyrum
pratense, which is found in clearings
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Adults require hot sunny clearings in woods for flight, mating &
oviposition
Historically, these were provided by the practice of coppicing –
different areas cut every year
By early 20th century, coppicing was no longer economic, & was
abandoned
Identification of this process had dual impacts:
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Showed a management practice that would correct the problem
Demonstrates a method of restoration for whole communities in the
English countryside dependent on rotational coppicing
Restoration programme in the 1980s was very successful
CASE STUDY: THE LARGE COPPER4
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Extinct in England due to removal of wetland
habitats in East Anglia
Research undertaken in Netherlands to
assess possibility of restoration in England
Males require open fen meadows with nectar
plants as territory – network of sites is
needed
Eggs laid on water dock (Rumex hydrolapathum) on habitat edges
in sunny areas. Not found in open areas of male habitats
Dispersal pattern indicates a mosaic of landscape habitats is
required for survival.
Currently sufficient foodplants, but insufficient male territory, & too
many movement barriers
Fen restoration project advocates restoration of areas of open fen &
reedland, which would also allow reintroduction of the species
Illustrates restoration must take into account landscape-level &
microhabitat requirements
IMPLICATIONS OF THESE EXAMPLES
 Autecolocial studies are necessary to reveal complex linkages between
species & environment
 These species-environment linkages are essential & must be studied before
carrying out restoration
 Where habitats are already influenced by human activities, monitoring &
study outcomes will affect long-term management processes
 Single species can act as the focus for restoration
 Often hard to carry out restoration due to lack of knowledge of the goal
 Endangered species within the habitat can act as a focus and show the
ecosystem function
 Flagship species also provide a public focus for the project
 Rare species challenge us to restore complex communities
 Complex life cycles & specific habitat requirements in micro- & macro scales
 By restoring habitat to near original status, other non-focus species will
benefit
 Single foci are often insufficient, but with several flagship indicators a
functional system can be constructed.
EASE OF RESTORATION: SOIL
Top and sub soil
removed
Top and sub soil
removed
VEGETATION
 Obviously linked to the soil development
 If soil is intact, then recovery should be relatively
simple, through a successional process.
 In extreme situations, recovery may be limited due to
depleted seed bank or changed soil status
 Most common method of accelerating restoration is
bypassing immigration process (may be slow if
isolated from colonisers
 Immigration rates affected by dispersal method and
propagule type
 Slow migrating species (eg legumes) can be
Beachfront revegetation in introduced manually, through collection of seed from a
Australia
donor site
 Seeds: large numbers possible
 Seedlings: higher survival rate, especially if viable sites identified5
 Saplings: god survival rate, large time and effort involved in growing
and transporting
 Nutrient status may require fertilisation – too much may favour grasses
POLLINATOR COMMUNITY
 Spread and success of many species depends on pollinator
presence (usually insects, sometimes birds/bats/rodents)
 Bumblebees required for some spring flowers, but they have a
limited foraging range
 If no neighbouring vegetation of the appropriate type, then
pollinators will be absent
 Initial restoration may have to focus on
species with generalist pollinators
 Synchrony of flowering & pollinator
activity is also a problem
 Handel (1997) advocated introducing
sequentially flowering species to ensure
pollen presence for pollinators
 May mean compromise between old &
new communities
CASE STUDY: HWANGE COAL MINE
 Mine tailings are carbonaceous shale (very high C content, smoulders
on contact with air)
 Tailings covered with subsurface soil from new opencast areas
 Soil pH ~3
 Initial process – cover sides of dumps with extra soil to prevent erosion
introducing air (subterranean burning); change slope angle
 Seed soil with pit ash from coal burning (ph~8). Approximately 3t/ha
required to increase pH to ~5
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Planting of low pH tolerant grasses
from local area to fix soil for
movement
Gathering of local tree/shrub seeds
Scarification, growth in nursery,
planting
Watering
Introduction of artificial wetland for
processing mine waste; clay-lined &
seeded with wetland species
CASE STUDY: HWANGE COAL MINE
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Natural succession process initiated.
Nearest natural habitat 1.2km over burning mine dumps!
Years 1-3: limited growth, periodic burning. Grasses successful
Year 4: shrubs increasing in coverage. Pitfall traps catch 15spp
ants, 20 beetles. >20 spp butterflies present
Year 5: Numbers of insects present increases, birds arrive as
trees grow.
Year 10: sample show >25 unseeded tree species, several
grasses. Baobabs transplanted!
Overall, the process was very successful
Caveat: Erosion is a big problem. Eventually pit slope walls will be
eroded, initiating large subterranean burns.
Solution: ensure slope vegetation is viable in the long term &
make end walls very thick. Provides time for leaching?
Functional ecosystem sitting on a time bomb
RESTORATION: PROS
 Can be carried out at all scales
 Large scale projects tend to be expensive
 allow whole landscapes to become functional ecosystems
 link conservation areas
 Small scale projects more common
 Opportunities for local involvement
 Provides education & highlights importance of ecosystem services
 Opportunities increasing in developed world:
 De-intensification of agriculture
 Abandonment of agricultural land
 Availability of post-industrial sites (often near cities
 Developing world:
 Additional opportunities for cultural preservation of land-based
cultures
 Environmental knowledge: people are less likely to degrade land
when they understand its worth
RESTORATION: CONS
 Generally very expensive, even in
comparison to establishment of
conservation areas
 Limits to what it can do – restoration is
not an exact science, and it is unlikely to
provide a fully-functioning ecosystem in
most cases
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Overly optimistic mitigation expectations allow
development to progress in sensitive areas
Last is very important, as offsets are often
provided for large developments
Environmental consultants who carry out EIAs
are developing expertise in restoration, & may
profit from mitigation measures
Claim that mitigation is viable without real
evidence
SUMMARY
 Protecting habitat is more effective than restoring it
 Offers positive action to repair some of the damage to
biodiversity
 Biggest challenge is understanding the complexity and
interactions of biodiversity and how to make them function
after disturbance
 Can be very beneficial to local communities, but can be
misused to argue for translocation schemes/ habitat
creation schemes with little chance of success
 Requires constant monitoring to assess success and
long-term management to assist in succession processes
 Should not be used as an excuse to allow development in
sensitive areas.