Transcript Chapter10

DEFINING RESTORATION
• Rehabilitation aims to revive important ecological services, or
to restore a natural dynamic to ecological communities.
• Rehabilitation is used to regain some but not all of the original
biodiversity of an area (WRI, 2003).
• It might mean to regain agricultural value or to vegetate with
species merely to have a natural system in place, (not
necessarily an indigenous system).
• Reclamation suggests bringing something back to its
original condition. It includes any process promoting soil
conservation and productive use of derelict land (Peterson
and Etter, 1970). The best methods use vegetation cover
that is self-renewing, attractive and long-term.
DEFINING RESTORATION
• Restoration aims at facilitating natural processes in
disturbed areas that will eventually lead to self-sustaining
ecosystems similar to what was present before
disturbance.
• Most complete restoration is rarely realistic because
determining the pre-disturbance state of most
ecosystems is difficult, and because ecosystems
continually change (WRI, 2003).
• Goal: return a habitat to a more desirable condition
involving a particular species composition, community
structure, and/or set of ecosystem functions.
• Revegetation means to establish a plant cover of any type
(Mentis and Ellery, 1994).
RESTORATION ECOLOGY
Benefits include:
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http://www.rioweb.org/
photogallery/boywithba
rrow.jpeg
• Restoration ecology aims to re-establish or rehabilitate
damaged or lost plant or animal populations or species
assemblages indigenous to the area of interest (Jordan et
al, 1987).
Relies on fundamental knowledge of the target
species, but it also provides opportunities for testing
basic ecological theories.
Maintenance of diversity of plants and animals
Improving wildlife habitats
Creating more aesthetically pleasing surroundings
Restoring natural communities
Protecting locally rare species
THE PLANNING PROCESS
• Setting realistic objectives is most NB step (Pastorok et al,
1997).
• In a mountain catchment, the most NB function may be to
supply clean water. Alien trees must be removed and indigenous
cover must be there to prevent erosion (Holmes and
Richardson, 1999).
http://www.cnpsyerbabuena.org/habitat_rest.html
• Less transformed sites - reintroducing missing plant species
• More transformed sites - reintroduce soil biota before some
species can establish (Holmes and Richardson, 1999).
• Realistic objectives consider extent of damage (caused by IAS
and the control or clearing of them), ecological potential, land-use
goals and socio-economic constraints (available funds, time and
trained staff).
http://ecology.ucdavis.edu/restoration/ec
ological_restoration.htm
• Landscape interactions must be considered.
MORE TO CONSIDER
• Restoration of disturbance processes must
include those to which the indigenous plants
are adapted (e.g. natural flooding, herbivory,
trampling).
• Restoration may require reintroduction or
management of the natural disturbance
regime, elimination of a damaging
anthropogenic disturbance regime, or
introduction of a new disturbance regime
(Pavlovic, 1994)
http://www.cnpsyerbabuena.org/habitat_rest.html
• There is an important relationship between
scale of disturbance and species abundance,
distribution and persistence (Pavlovic, 1994)
REVEGETATION
• Planned disturbances are often accompanied by revegetation
plans.
• Topsoil is frequently collected and stored, to be replaced at the
surface during revegetation. This practice is important for
restoring the indigenous seed bank and soil microbial
community.
• The longer the time that topsoil is stockpiled, the more likely it
is that viable seeds of indigenous species will decline. Many
harmful alien species have persistent seed banks.
http://www.eroresources.com/ser
vices/Restore.htm
Ecosystem
condition
Aim
Example
Actions
Evaluation
Most pristine
Maintain or
enhance local
biodiversity
Locally extirpated
species
Sow seed of desired
species, or transplant
seedlings, after disturbance
Monitor
establishment &
survival of
introduced species
Vulnerable species
As above
As above
Non-local indigenous
species
Remove planted indigenous
species & their hybrids
Monitor sites for
non-local species &
their hybrids
Invasive alien species
Remove alien species
Monitor sites for
alien species
Young, dense stands of
alien species
Remove alien plants & burn
Monitor species
recruitment i.t.o
diversity, guild
structure & canopy
cover
Old, dense stands of
alien species
Remove alien plants & burn;
sow locally collected
indigenous species
Monitor species
recruitment i.t.o
diversity, guild
structure & canopy
cover
Re-establish
ecosystem
diversity, structure
and function
Ecosystem
condition
Aim
Re-establish
indigenous plant
cover
Improve remnant
connectivity
Highly
degraded
Establish plant
cover
Example
Actions
Evaluation
Old, dense alien stands with
evidence of soil damage
Remove alien plants & burn;
stabilize slopes against further soil
erosion; sow locally collected
indigenous species
Monitor species
recruitment &
soil erosion
Denuded & eroding
footpaths
Reconstruct footpath & stabilize
surrounding slopes; plant denuded
areas with local seedling material in
winter; sow with locally collected
species after disturbance
As above
Revegetation following
mining or other short-term
construction operations
Replace topsoil; sow with suitable
seed mix
Monitor
indigenous
plant cover &
alien species
Grassy road verges with
potential to become
indigenous vegetation
corridors
Remove non-indigenous cover
(herbicide as last resort); sow or
plant with suitable indigenous
species
As above
Creation of indigenous
vegetation corridors in
agricultural land
As above
As above
Stabilise slopes after road
construction
If little topsoil is available, add mulch
& sow with fast-growing noninvasive alien annuals; oversow with
indigenous seed
Monitor plant
cover & alien
species
ROLE OF IAS IN RESTORATION (D’Antonio and Meyerson, 2002)
• IAS may be part of the reason or need for restoration
• IAS may be the first to re-colonize after disturbances
associated with vegetation removal (unplanned or “natural”
disturbance)
• IAS may be the first to colonize after a planned disturbance,
even if they were not present in the pre-disturbance
community, and may interfere with restoration efforts
• IAS may leave behind a legacy after removal that makes
long-term restoration difficult (e.g. seed bank, chemical or
physical alteration of the habitat)
• Alien spp. may be used in restoration to restore particular
functions if indigenous spp. aren’t suitable or available
LONG-TERM EFFECTS OF IAS
• Myrica faya has colonized young volcanic soils in Hawaii, where
fixes nitrogen at a rate four times as high as all other sources of
fixation combined. When it is killed, it leaves a legacy of high
soil nitrogen. Introduced grasses appear to benefit from this dieoff, complicating restoration efforts (Adler et al, 1998).
• Invasive alien species often have very large persistent seed
banks. They often maintain a much larger seed bank in their new
habitat. Species with buried seed banks or extensive and
persistent rhizomatous networks require repeated follow-up
treatments (D’Antonio and Meyerson, 2002).
LONG-TERM EFFECTS OF IAS cont.
• In South African riverbanks, erosion has been accelerated by
many introduced species (Acacia and Pinus spp.).
• Restoration of sites degraded by alien species and soil erosion
pose a particular challenge.
• The topography may no longer resemble the pre-invasion
conditions, and removal of the aliens may cause further erosion.
• Highly degraded sites may no longer be able to support the
desired species assemblages. Under these conditions it may be
necessary to stabilise the soil using synthetic or biodegradable
materials or establish indigenous vegetation before alien
removal (D’Antonio and Meyerson, 2002).
THE ROLE OF IAS IN RESTORATION
• In some degraded sites it may be necessary to introduce an
alien species to assist with the restoration process.
• Where soil erosion or the potential for it is severe, many
practitioners use fast-growing but sterile alien grasses to
quickly establish cover. These grasses do not seed and
presumably give way to indigenous species (D’Antonio and
Meyerson, 2002).
• Introduced species used in restoration must be monitored over
time, and only used if no other options.
• Introduced species do sometimes have a role to play in
restoring functional aspects of ecosystems, but this must be
related to the overall goal of restoration and the context within
which restoration is carried out (Hobbs and Mooney, 1993).
Chapter 1 Definitions
Chapter 2 History, globalisation and GMOs
Chapter 3 The human dimension
Chapter 4 Pathways of introduction
Chapter 5 Characteristics of invasive alien species
Chapter 6 The ecology of biological invasions
Chapter 7 Impacts of invasive alien species
Chapter 8 Invasive species management
Chapter 9 Predicting invasive spp. occurrence and spread
Chapter 10 Ecological restoration
Next
Chapter 11 International perspective
Chapter 12 South African perspective
I hope that you found chapter 10 fun to do and that you
will enjoy the next chapter in this course.