| Introduction
Map
The Horsey Creek ecosystem-based analysis, along with its associated
report and maps, was created to provide information to local residents
and groups who wish to protect, maintain, and plan for the ecologically
sustainable use of the forests and waters of this section of the
Fraser River Headwaters. The Horsey Creek analysis is part of
an ongoing project to analyze the entire Fraser River Headwaters
and to provide ecological connectivity between major park reserves,
including Mount Robson and Wells Grey Provincial Parks.
The main objectives
of this analysis were to:
* Identify important landscape and ecosystem characteristics,
assess ecological sensitivity.
* Assess how past and present human use has affected the ecological
condition of the landscape.
* Develop recommendations to guide the protection, maintenance,
and sustainable use of the Horsey Creek Landscape.
The study
area (see map) is approximately 150,000 hectares comprising the
wide floodplain, terraces, and valley walls of the Fraser River
in the Robson Valley, and its steep tributary watersheds in the
Cariboo and Rocky mountains. Elevation ranges from 730 to 3500
meters, and more than 40% of the study area is comprised of alpine
tundra.
At lower elevations
the climate of Horsey Creek varies from a mean daily maximum of
24°C in July to a mean daily minimum of -14°C in January.
Its high mean annual precipitation of 700-800 mm creates a productive
"interior rainforest" ecology. Higher elevation ecosystems
are less productive and are limited by a shorter growing season
(due mainly to cooler temperatures and up to 5 meters of snow).
Ecological Characteristics
Map
The Horsey Creek area contains a gradient of ecological associations
that change with elevation from the valley floor to the alpine
slopes and meadows. The ecosystems on the northeast side of the
trench are also adapted to slightly colder and drier conditions
than those on the southwest side.
The biogeoclimatic subzones (see map) identify four different
ecosystems. The Dry Hot Sub Boreal Spruce (SBSdh) subzone occupies
the relatively dry and warm floodplain terraces and lower slopes
of the Robson Valley. This subzone contains scattered, even-aged
stands of douglas fir and lodgepole pine, as well as veteran patches
of old-growth douglas fir, interspersed within a matrix of white
spruce and subalpine fir. The Moist Mild Interior Cedar-Hemlock
(ICHmm) subzone occupies slightly colder and higher slopes on
either side of the trench, and contains a complex structured forest
dominated by western redcedar hemlock, with minor components of
white spruce and subalpine fir. The Moist Mild Engleman Spruce-Subalpine
Fir (ESSFmm1) subzone is common in the wetter, colder, middle
and upper elevations. The upper elevations are dominated by alpine
tundra.
Within these biogeoclimatic subzones are several rare plant associations.
While these communities are marginally productive from a timber
management point of view, they provide important wildlife habitat.
More than 50 mammal species occur in the Horsey Creek Landscape,
including four that are at risk due to human disturbance and are
blue-listed (grizzly bear, wolverine, rocky mountain bighorn sheep,
and fisher). Also at risk are three bird, one fish, and sixteen
plant species.
Ecological Sensitivity to Disturbance
Map
The
indicators used to determine ecological sensitivity to disturbance
(ESD) include:
* Proximity
to rivers, lakes, streams, and wetlands
* Slopes in excess of 60% and avalanche zones
* Complex, highly variable terrain containing more than 50% rock
outcrops, steep gullies, slides, and fallen rock
* Thin, poorly-developed soils that cover bedrock, fallen rock,
and coarse glacial materials
* Very wet or very dry site moisture conditions
* High elevations or cold temperatures that reduce productivity.
These criteria were used to identify the following ESD classes:
Riparian
Ecosystems and Wetlands: Riparian ecosystems include the riparian
zone and the riparian zone of influence. These are areas adjacent
to streams, rivers, lakes, and wetlands situated in depressions
or valley bottoms. These areas provide a high level of biodiversity,
play a crucial role in regulating water flows and water quality,
and provide corridors for plants and wildlife.
Alpine: Alpine areas contain extremely sensitive ecosystems
which are limited by cold temperatures and a very short growing
season.
Avalanche Terrain: Avalanche terrain consists of steep,
narrow chutes which experience snow avalanches, limiting vegetation
to a hardy shrub layer.
Complex Terrain: Terrain is considered complex when it
contains highly variable topography containing rock outcrops,
steep gullies, slides, and fallen rock.
Steep Terrain: An area is considered steep if it has slopes
greater than 60%. Steep slopes are prone to landslides and erosion
when subjected to road construction and logging.
Moderately Stable Terrain: Areas with an average slope
between 30% and 60% are considered moderately stable. Small areas
with rocky knolls, steep slopes, or wetland depressions may occupy
up to 50% of the terrain, but overall slopes contain well-developed,
productive soils.
Stable Terrain: Stable terrain consists of slopes less
than 30% and well-drained, productive soils.
Landbase
Unsuitable for Development
Map
Areas that are unsuitable for development (see map) are either
where timber management and forest uses are not appropriate because
the sites do not support forest vegetation, or because they are
highly sensitive to disturbance. While some areas are designated
as unsuitable for development, it does not mean that they are
unusable for all human activities, such as recreation and nature
interpretation.
The MoF forest
development and timber supply planning procedures first identify
the "forest landbase"—the amount of forested public
land. They then apply a variety of criteria to identify forest
landbase "netdowns"-- areas that are subtracted from
the timber landbase—such as non-forested, non-productive,
non-merchantable, or environmentally sensitive areas.
This map combines
Ministry of Forests (MoF) designations with SFF's ecological sensitivity
to disturbance ratings. This is done to clearly show areas of
agreement and areas of difference. The Silva Forest Foundation’s
ecological sensitivity analyses add to the MoF designations because
SFF uses more stringent definitions of ecological sensitivity
than the MoF (see chart).
Landbase Unsuitable for Development classes include:
* MoF Non-Forested Areas: These areas include water features,
rock outcrops, alpine tundra, wetlands, private property, and
agricultural clearing.
* MoF Private Property.
MoF Netdowns include:
* Environmentally Sensitive Area Class 1 and 2. These are areas
with significant non-timber values, fragile and unstable soils,
or regeneration problems.
* Inoperable areas. Inoperable areas are considered uneconomic
to harvest.
* Non-Merchantable Forest. These are stands of non-merchantable
deciduous trees such as aspen and black cottonwood.
* Low Site Index. These are areas with low timber growing potential.
* Inaccessible Areas. These areas are difficult to reach and considered
uneconomic to harvest.
SFF Ecologically Sensitive Netdowns include:
* Silva Riparian Zones: This class contains wetlands and riparian
ecosystems.
* Silva Ecologically Sensitive. This class combines steep terrain,
complex or broken terrain, and areas of shallow soils.
Landscape
Development
Map
Landscape
development refers to how past and present human activities have
affected the landscape. Industrial development in the lower elevations
(within the Robson Valley) began in the 1900’s and had profound
impacts on landscape pattern, forest composition, habitat availability,
stream integrity, and wildlife abundance. These impacts were caused
by a combination of land clearing for rail and roads, agriculture,
and settlement, and it consisted of both logging activities and
human-caused fires.
Lower elevation
forests were all but eliminated. The multi-aged mosaic that included
old growth lodgepole pine and Douglas fir on drier sites, white
spruce and subalpine fir on moist sites, and western redcedar
and black cottonwood on wet sites, gave way to a patchwork legacy
of roads, fields, and fragmented young forests. The combined impact
of this forest conversion was likely devastating to wildlife,
leaving little old growth and riparian-forest dependent species,
and leaving little low-elevation habitat and few corridors.
Industrial
development since then has had an equally significant impact on
landscape and site ecology. Natural disturbances such as stand-replacing
fires have been suppressed. Human disturbances have included clearcut
logging and fire escapes from slashburning. The result has been
both altered species composition and age-class distribution of
the Horsey Creek forests. Logging has also eliminated substantial
lengths of riparian forests, and associated road construction
has altered ground and surface water flows, interrupted wildlife
travel routes, and created unnaturally high levels of forest edge.
The map shows
the location of proposed logging cutblocks as well as the extent
of the direct, apparent impacts of past logging that has occurred
over the last 40 years within the Horsey Creek landscape.
While it isn't displayed here, a map overlay (a see-through map
that can be placed over other maps to present additional information)
was also created depicting "zones of influence," also
known as the edge effects, of past and proposed logging (see map).
Zones of influence are areas within forest stands that are impacted
by outside activities, such as logging roads and clearcuts. Physical
impacts include changes in air temperature, soil temperature,
humidity, and solar radiation. Biological impacts include changes
in species compositon, species structure, and population dynamics.
Zones of influence for different impacts usually extend from as
little as 1 meter up to 500 meters. Some impacts occur at an even
greater distance; spotted owl reproduction, for example, can be
affected up to 1.1 kilometers. Appendix V of the Horsey Creek
Landscape Report, "Assessing the Ecological Impacts of Timber
Management: Apparent Impacts, Actual Impacts, and Precautionary
Forest Development," describes and references studies on
specific impacts.
Old Growth Forests
Map
Ecological
research over the past two centuries has transformed our understanding
of the role that old growth forest stands and large old trees
play in overall landscape and ecosystem function.
At the landscape
level, patches of old growth provide critical habitat requirements
for such species as deer and elk in winter. Many plant, small
amphibian, and invertebrate species also depend on the moist,
moderated "interior" climate found only within old growth
forests during summer months. Old growth forests usually contain
a higher level of biodiversity than younger forests and provide
habitat for many old growth dependent plant and animal species.
At the stand scale, the structural diversity—small and large
diameter trees, snags, and downed logs, as well as multi-layered
canopies—common in many old growth forests is not found in
younger and planted forests.
The distribution
of remaining old growth forests in the Horsey Creek landscape
(see chart) was created from a combination of the MoF forest cover
databases and aerial photo interpretation. The MoF datasets used
were stand height, age class, and dominant tree species combinations.
While this data is designed to identify specific stands of old
trees by species type, they may not be a completely reliable indicator
of fully functioning old growth forests.
Clearly, the majority of remaining old growth forests lie in the
tributary watersheds, while only few remain in the Robson Valley
section (within private land). Conservation easements or land
trusts should be considered as a means of protecting these remnant
stands. The majority of remaining old growth forests are also
dominated by engleman spruce and subalpine fir. Douglas fir, western
redcedar, and western hemlock old growth stands, which used to
be common at lower elevations in the Horsey Creek landscape, now
occupy less than 1% of the landscape. Indeed, nearly all old growth
forests have been eliminated from the floodplains, terraces, and
lower slopes on either side of the Fraser River, as well as from
the most productive valley bottom sites in the Horsey Creek Landscape.
Human
Uses
Map
Current human uses (see map) in the Horsey Creek Landscape include
continued settlement and agriculture on private lands located
on the Fraser River floodplain terraces, a small amount of logging
in the Small and Horsey Creek watersheds, and backcountry recreational
activities in portions of all tributary watersheds. Grazing leases
are used in the Kiwa, Small, and Horsey Creek Watersheds.
Settlement
in the Robson Valley remains sparse, but the amount of land cleared
for development and agriculture increased in recent years. Forests
regenerating on unused private lands are beginning to recover
structural characteristics such as mature trees, snags, and downed
logs.
Protected Landscape Network
Map
Undisturbed
forest landscapes contain a spatially diverse and a temporally
variable mosaic of ecosystems and habitats. Conventional timber
management and other development activities typically impose disturbances
and create landscape patterns that differ ecologically from those
that occur naturally.
The purpose
of a protected landscape network (PLN) is to maintain, and, where
necessary, restore important patterns and processes that sustain
the ecological functioning of the landscape. A PLN maintains these
components as a permanent mosaic of ecological reserves that can
only be used for non-extractive activities such hiking, and for
“light impact” extractive activities (such as wild mushroom
harvesting) where appropriate.
The network
of connecting corridors and small protected areas that are added
to the sensitive areas are designed using air photo interpretation,
GIS analysis, and knowledge of landscape ecology and habitat requirements.
The Horsey
Creek PLN (see map) is designed to protect and maintain landscape
function by including six key ecological components in the design
process:
1. Regional Connectivity
The two major protected areas in the region encompassing the Horsey
Creek Landscape are Robson Provincial Park to the east, and Wells
Grey Provincial Park to the southwest. The proposed landscape
network establishes connectivity between these existing protected
areas and the Horsey Creek landscape.
2. Landscape
Corridors and Connections
Connectivity within the Horsey Creek landscape is provided by
riparian and cross-valley corridors. The landscape connections
are designed to take advantage of topography, land owership, and
ecological features that do allow movement across the landscape.
3. Old
Growth Reserves
As shown in Figure 6, past development and recent logging has
eliminated most of the old growth forests on stable and moderately
stable terrain in the Horsey Creek Landscape. The old growth reserves
that are included in the PLN are designed to maintain what is
left of the natural distribution of stand age classes across the
landscape:
4. Old
Growth Recruitment Areas
Restoring a natural distribution of stand age classes within the
Horsey Creek Landscape will involve recruiting old growth compositional
and structural characteristics within existing younger forest
stands.
5. Rare
Ecosystems and Biodiversity "Hotspots"
In addition to the rare old growth forests on stable terrain discussed
above, the rare ecosystems and biodiversity hotspots within the
proposed protected landscape network include riparian zones, wetlandsm,
and the Tete Creek Corridor.
6. Habitat
for Rare and Endangered Species
The field studies necessary to identify habitat for rare, threatened,
or at risk species and plant communities were beyond the scope
of this project. The PLN is designed with the intention of providing
a general measure of protection for a broad range of threatened
species. As the location of threatened animal, plant, and plant
communities are identified, additional reserves can be included
in the PLN.
Potential
Timber Management
Map
Chart
The final step in ecosystem-based landscape analysis involves
identifying where and when a variety of ecologically responsible
forest use activities can occur in areas that lie in between the
components of the protected landscape network. Forest use activities,
whether timber cutting, commercial tourism, watershed protection,
or botanical forest products harvesting, must be caefully planned
and executed to ensure the protection and maintenance of fully
functioning ecosystems.
Human use
areas commonly identified in an ecosystem-based analysis include:
First Nations Cultural Areas. These zones are identified
and planned for in consultation with individual First Nations
groups.
Ecotourism Areas. The priority use for these areas is ecologically
responsible activities such as wildlife viewing, bird watching,
backpacking, kayaking and canoeing, guide-outfitting, and so on.
Wildcrafting Areas. Harvesting edible plants, mushrooms, medicinal
herbs, and other non-timber forest products is the priority in
these areas.
Watershed Protection Areas. Watershed protection zones
are often established in the headwaters of streams that are used
as sources of domestic, community, or agricultural water.
Ecosystem-based Timber Areas. Timber cutting can occur
in areas of stable or moderately stable terrain. Within stable
and moderately stable terrain, logging systems are designed to
maintain or restore the ecological integrity of the forests.
The map shows the location of potential timber management areas
within the Horsey Creek Landscape, and the amount of forest land
in each of these zones is summarized in the table. The potential
timber management areas include:
Restoration
Zones ES are ecologically sensitive areas that have been clearcut
in the recent past. These areas will become part of the protected
landscape network as restoration proceeds.
Restoration Zones MS are areas on moderately stable and
stable terrain that contain clearcuts or stands that have been
high-graded. These zones are located on productive sites, and
can be considered for partial cutting following site assessment
and sufficient time to allow for restoration of natural composition
and structure.
Potential Timber Management Zones are areas containing
productive young, mature, and unprotected old growth forests located
on stable and moderately stable slopes. Partial cutting can be
carried out in these areas following the preparation of an ecologically
responsible cutting rate for the Horsey Creek Landscape.
Funding
for this project was provided by the W. Alton Jones Foundation. |
