 Conference
1999
New Zealand Plants and their Story
New
Zealand Forest Remnants and Their Story:
A Background to Their Management and Restoration
Paul
Blaschke
Boffa Miskell Ltd
Box 11 442
In this talk I introduced
some ideas intended to give a useful background for understanding,
managing and restoring forest remnants. These ideas are briefly
summarised below. I also offer a selected bibliography of key references
and further reading suggestions for following up the themes of this
summary.
What is a forest remnant?
Some definitions:
". The little that remains,
small remaining quantity or piece or number of ... things; surviving
trace, fragment, scrap." (Oxford English Dictionary).
"... A patch of native
forest around which most or all of the original vegetation has been
removed." (Bruce Burns, Landcare Research).
Some general characteristics
of forest remnants arising directly from these definitions include:
- Size: Forest remnants
are usually thought of as small areas but almost all areas of
forest in New Zealand are remnant, so not all New Zealand forest
remnants are small!
- Discreteness: Remnants
are surrounded by some other different vegetation.
- History: A remnant's
existence arises from non-natural processes.
Ecological characteristics
of forest remnants
Ecological characteristics
of forest remnants arise from their general nature as indicated
above. Forest remnants share some environmental characteristics
with their surrounding habitats (usually called the "matrix"), but
the above characteristics also make them different. They are strongly
affected by many outside influences, and many of their characteristics
are affected by their small size relative to their surrounding matrix.
Biota
Forest remnants usually
contain a restricted number of species. These species may not be
representative of the whole ecological unit in which they occur
(e.g., the Ecological District), and may have limited genetic diversity.
Species populations are thus not natural, and are frequently regenerating
from external or natural disturbance. Populations may have fragmented
age or size characteristics, e.g., they may frequently be even-aged
("cohort" populations).
Plants and animals alike
may face external barriers to reproduction and/or dispersal, and
plant populations may need external dispersal agents. On the other
hand, when forest remnants occur in relatively species-rich lowlands,
they may have more diversity than even larger forest areas elsewhere
(e.g., at higher altitudes).
Environmental
At the margin between
the forest remnant and its surrounding matrix, there is usually
an abrupt transition between the two areas: this results in abrupt
changes of light levels, humidity, temperature, soil moisture, etc.
"Edge effects" dominate ecological processes in a large proportion
of remnants, especially small ones. However, there is very often
a transition or buffer zone. Remnants are often severely affected
by weeds and pests, especially if unfenced. This may be because
of edge effects, because they are weakened by exposure, or because
they offer a relatively favourable habitat to weeds or pests compared
to the surrounding matrix. In New Zealand, forest remnants are most
often surrounded by scrub, introduced grassland or exotic tree plantations,
less often by native tussock grassland or other vegetation. These
different types of vegetation have greatly different characteristics
as physical buffer zones and as sources of weeds and pests in the
remnants.
Summary and Implications
of Ecological Characteristics:
Most forest remnants
have limited biodiversity, and limited environmental resilience.
This means that they often need intensive management if they are
to remain viable. But minimum size thresholds for long-term viability
of remnants are not well known. These thresholds are likely to differ
according to the composition and environment of the remnant.
Why are forest remnants
important?
Forest remnants perform
a varied range of valued functions and services:
- Refuges for native
biodiversity, especially in the lowlands
- Wildlife corridors
- Contribute ecosystem
services
- Preserve representative
soil types
- Snapshots of the
past
- A context for understanding
and appreciating biodiversity
- Contribute to New
Zealand's landscape character
- Cultural importance
to Maori and pakeha.
Remnants in urban areas
are particularly important, because they may be the only natural
areas in the urban setting, and are the natural areas which most
people experience and enjoy most of the time. Therefore urban forest
remnants not only have the above values but also important amenity
values as well. As such, they are becoming the focus of much restoration
and management effort, especially by community groups and local
authorities.
Conservation of forest
remnants symbolises a current shift in thinking about nature conservation
in New Zealand. Management of large tracts of publicly-owned, remote
near-wilderness natural areas (which do not represent all of New
Zealand's total biodiversity) by the Department of Conservation
is no longer the sole focus of effort. Much more emphasis is now
going into people and communities conserving remnant natural areas,
often council reserves or privately owned, near where they live.
Such remnants preserve a wide range of biodiversity and are in fact
probably the most significant reservoirs of biodiversity in lowlands
(including rare and threatened biodiversity) in most regions of
the country. This shift is becoming recognised in government policy,
especially the New Zealand Biodiversity Strategy.
Management and Restoration
of Forest Remnants
In my opinion, restoration
is a subset of management, and all management should relate strongly
to sustainable land management principles. There are three interrelated
aspects of sustainable land management generally — ecological,
economic and social. For forest remnant management I would summarise
these into "three Ps":
Processes (ecological)
The key is to maintain
essential ecological processes in order to maintain the ecological
health of the remnant, and the ecological integrity of the remnant
within its matrix. Maintaining the ecological processes of the buffer/edge
zone is often a crucial part of this; understanding the ecological
character and processes of the buffer zones and at least the immediate
matrix are thus as important as understanding the remnant itself.
Priorities (economic)
Most managers don't have
the resources to do everything desirable. They need to prioritise
actions in order to maintain the ecological processes. Prioritising
actions (often relating to different parts of the forest remnant,
i.e., a zoning approach) is more important than prioritising areas,
especially in urban situations where amenity values are often as
high or higher than biodiversity conservation values. Monitoring
environmental outcomes of management actions is an important element
in sorting out management priorities.
People (social)
People may have been
the cause of forests becoming remnants but they also allow forest
remnants to survive now. People are the greatest resource for forest
remnant management; they provide the direct link to the local importance
of forest remnants. There is a tremendous surge of interest and
commitment to maintenance and restoration of all kinds of remnants.
Supporting this local voluntary effort is probably the most important
way that government can make a difference.
Key references and further
reading
Brockie, R. 1992: A
Living New Zealand Forest. David Bateman, Auckland.
Burns, B., Barker, G.M.,
Harris, R.J. and Innes, J. in press: Conifers and cows: forest survival
in New Zealand dairy landscape. In: Saunders, D. Craig,
J.L and Mitchell, N.D., Nature Conservation in Production Environments.
Nature Conservation 5, Surrey Beattie, Sydney.
Crisp, P.N., Dickinson,
K.J. and Gibbs, G.W. 1998: Does native invertebrate diversity reflect
native plant diversity? A case study from New Zealand and implications
for conservation. Biological Conservation. 83: 209-220.
Davies-Colly, R.J., Payne,
G.W and van Elswijk, M. 2000: Microclimate gradients across a forest
edge. New Zealand Journal of Ecology. 24: 111-122.
Department of Conservation
and Ministry for the Environment 2000: The New Zealand Biodiversity
Strategy. Department of Conservation, Wellington.
Department of Conservation
(Auckland Conservancy) 1996: Conservation Management Strategy
for Auckland. Department of Conservation, Auckland.
Environment Waikato 2000:
Waikato State of the Environment Report. Environment Waikato,
Hamilton.
Handford, P. 2000: Forest
monitoring handbook. Forme Consulting Group, Wellington.
Harris, R.J. and Burns,
B. 2000: Beetle communities of kahikatea forest patches in a pasture-dominated
landscape. New Zealand Journal of Ecology. 24: 57-68.
Kuschel, G. 1990: Beetles
in a suburban environment: a New Zealand case study. DSIR Plant
Protection Division, Auckland.
Meurk, C.D., Ward, J.C.
and O'Connor, K.F. 1993: Natural Areas of Christchurch: Evaluation
and Recommendations for Management as Heritage. Report for
Christchurch City Council. Centre for Resource Management, Lincoln.
Ministerial Advisory
Committee 2000: Bio-What? Addressing the effects of private
land management on indigenous biodiversity. Preliminary report.
Ministry for the Environment, Wellington.
Ministry for the Environment
1997: The State of New Zealand's Environment. Government
Printer, Wellington.
Norton, D.A. 1997. Ecological
basis for restoration in mainland New Zealand. Pp.11-14 in:
Smale, M.C. and Meurk, C.D. (comps): Proceedings of a Workshop
on Scientific Issues in Ecological Restoration. Landcare Research
Science Series No 14.
Park, G.N. 1999: An
Inventory of the Surviving Traces of Primary Forest of Wellington
City. Report for Wellington City Council. Wellington City Council.
Porteous, T. 1993: Native
Forest Restoration: a practical guide for landowners. Queen
Elizabeth II National Trust, Wellington.
Simpson, P: 1997: Ecological
Restoration in the Wellington Conservancy. Department of Conservation,
Wellington.
Smale, M.C. and Meurk,
C.D. (comps) 1997: Proceedings of a Workshop on Scientific Issues
in Ecological Restoration. Landcare Research Science Series
No 14.
Top
of page
|
