​Habitat Suitability Model

The data

The datasets collected for the MCE were downloaded from the BCData Catalogue and the BC Commission for Environmental Cooperation, in both vector and raster format. All of our data was in the projected coordinate system NAD_1983_BC_Environment_Albers and the Albers projection. The raster cell size was 1,000m by 1,000m, and the extent of each layer was set equal to one another. 

 

Criteria

Variables influencing Mountain Caribou habitat location were determined from a literature search. Mountain Caribou depend on lichen that grow on trees as their primary winter food and spend winters at higher elevation in old growth forests (BC Gov., 1999). Deep snow accumulation is an impediment to digging through the snow for food. If the snowpack is firm enough, caribou will stand on top to reach lichen growing on trees. It takes time for trees to develop heavy loads of arboreal lichen; as a result, only very old forests provide abundant lichen (Ibid.). Large patches of old growth forests also allow caribou to avoid predators, such as wolves, cougars, and bears. The Mountain Caribou’s range includes both rugged peaks and more gentle highland terrain, with preferences for Boreal Altai Fescue Alpine (BAFA), Englemann Spruce-Subalpine Fir (ESSF), Interior Cedar-Hemlock (ICH), and Sub-Boreal Spruce (SBS) biogeoclimate zones (Ibid.). Mountain Caribou prefer higher elevations, but are limited by glaciers on the highest peaks. Caribou also tend to avoid human populated places and can be disturbed by highways, railroads, forestry roads, and snowmobile trails. They cannot live on certain land use areas, such as agricultural, urban, mining or residential areas. Even though they are agile climbers, caribou cannot live on extreme slopes. 

 

Data Preparation

Factors influencing caribou habitat preference include biogeoclimate zone, land use, forestry roads, railways, highways, and slope. There are no human populated regions, airports, or snowmobile trails within the study area. Slope was calculated from the DEM using the Spatial Analyst "Slope" tool.  Shapefiles were downloaded and clipped to the designated study area, using the "Extract by Mask" tool for rasters and the "Clip" tool for vectors. Multi-ring buffer layers were then created around the forestry roads, highways, and railroads using the "Multiple Ring Buffer" tool; the more remote the area is, the less anthropogenic impact on the caribou.

 

Reclassification

In order to normalize the data for the MCE, we assigned a value from 0 - 1 to each of the factors within the layers, with 0 representing the least suitable habitat for caribou, and 1 representing the most suitable habitat. For the classification of continuous data, the Spatial Analyst “Fuzzy membership - linear" tool was used.  This produced layers of continous data with values from 0 - 1, and was used on the elevation, slope, forestry roads buffer, and railways/highways buffer.  For sets of discrete data, values of 0 - 1 were assigned in the attribute tables, depending on the impacts to caribou habitat suitability. These assigned values are shown in the tables below for the BEC zone and land use layers. Once all of the layers were reclassified, an MCE could be carried out. 

 

 

Biogeoclimate (BEC) Zone

 

BEC Zone CODE	BEC Zone NAME	Rating
BAFA	Boreal Altai Fescue Alpine	1
BWBS	Boreal Black and White Spruce	0.2
CMA	Coastal Mountain Heather Alpine	0.6
CWH	Coastal Western Hemlock	0.4
ESSF	Englemann Spruce-Subalpine Fir	1
ICH	Interior Cedar-Hemlock	1
IDF	Interior Douglas-fir	0.2
IMA	Interior Mountain-heather Alpine	0.6
MH	Mountain Hemlock	0.8
SBS	Sub-Boreal Spruce	1

 

 

Land Use

 

Code	Land Use type	Definition	Rating
AGR	Agriculture	Land based agricultural activities undifferentiated as to crop (ie. land is used as the producing medium).	0
ALP	Alpine	Areas virtually devoid of trees at high elevations	1
BARE	Barren surfaces	Rock barrens, badlands, sand and gravel flats, dunes and beaches where unvegetated surfaces predominate	0.2
EST	Estuaries	Salt water mud flats and intertidal areas at the mouth of rivers and creeks where the vegetation is influenced by frequent flooding (at least yearly).	0.2
WFRE	Fresh Water	Fresh water bodies (lakes, reservoirs and wide portions of major rivers).	0
ICE	Glaciers and Snow	Glaciers and permanent snow. Depending on the date of imagery, ephemeral snow may be included in this class.	0.6
MINE	Mining	Land used now (or in the past and remains unreclaimed) for the surface extraction of minerals or quarry materials.	0
FO	Old Forest	Forest greater than or equal to 140 years old and greater than 6 meters in height. Areas defined as Recently Logged and Selectively Logged land uses are excluded from this class.	1
OUT	Outside BC	Land outside British Columbia.	0.4
RANG	Range Lands	Unimproved pasture and grasslands based on cover rather than use. Cover includes drought tolerant grasses, sedges, scattered shrubs to 6 metres in height and less than 35% forest cover. Sparse forest stands are included with their understorey of drought tolerant shrubs and herbs	0.8
BURN	Recently Burned	Areas virtually devoid of trees due to fire within the past 20 years. Forest less than or equal to 15% cover.	0.4
LOG	Recently Logged	Timber harvesting within the past 20 years, or older if tree cover is less than 40% and under 6 metres in height.	0.4
REC	Recreation Activities	Land used for private or public outdoor recreational purposes. Ski resorts and golf courses are included. This class does not include recreational areas within built-up portions of cities, towns and villages, which are mapped as urban areas. This class includes waterfront cottage areas if they are at least 200 metres wide.	0
AGMX	Residential Agriculture Mixtures	Areas where agriculture activities are intermixed with residential and other buildings with a building density of between 2 to 0.2 per hectare.	0
SALT	Salt Water	Salt water bodies (ie oceans).	0
LOGS	Selectively Logged	Areas where the practice of selective logging can be clearly interpreted on the Landsat TM image and TRIM aerial photography.	0.6
SHR	Shrubs	Land where vegetation is dominated by shrubs, often also including grasses, herbs and geophytes.	0.8
AVA	Sub alpine Avalanche Chutes	Areas below the tree line that are devoid of forest growth due primarily to snow avalanches. Usually herb or shrub covered.	0.4
URB	Urban	All compact settlements including built up areas of cities, towns and villages as well as isolated units away from settlements such as manufacturing plants, rail yards and military camps. In most cases residential use will predominate in these areas. Open space which forms an integral part of the urban agglomeration, e.g. parks, golf courses, etc. are included as urban.	0
WET	Wetlands	Wetlands including swamps, marshes, bogs or fens. This class excludes lands with evidence or knowledge of haying or grazing in drier years.	0
FY	Young Forest	Forest less than 140 years old and greater than 6 metres in height. Areas defined as Recently Logged and Selectively Logged land uses are excluded from this class.	0.8

 

 

 

Multi-Criteria Analysis

All of the vector layers were converted into rasters using the “Feature to Raster” tool. After normalization, an MCE was carried out with the "Weighted Sum" tool. An MCE map was then produced using the assigned weights included in the table below. These values were arbitrarily chosen based on background knowledge of the impacts of these factors on caribou habitat preference. The higher the percentage, the more the variable impacts habitat suitability. An equally-weighted MCE was produced as a baseline for the sensitivity analysis, in order to show how the results would vary had another weighting system been used.

 

Layer	Rank
BEC Zone	40
Land Use	20
Slope	15
Elevation	15
Forestry Roads	5
Highways/Railroads	5

 

 

Forecast Model

In order to determine the effects of climate change on caribou habitat, an additional MCE analysis was carried out for a forecasted model. This MCE analysis was performed by substituting the present BEC zone layer for the predicted 2080 BEC zone layer. The forecast model was based only on the projected BEC zones, because this factor is the most important in terms of Mountain Caribou habitat preference and shows an evident change over the years due to climate change. Even within an 80 year period, there is significant change to the BEC zones present within the study area. A sensitivity analysis was carried out on the two forecast MCE maps.

 

Sensitivity Analysis

Sensitivity analysis is crucial to an MCE analysis, as it shows whether the chosen weights are biased or appropriate. The “Weighted Sum” tool was used to combine the weighted MCE and the equally weighted MCE for the present and future model. This produced maps with attribute data ranging from 0 - 3, with 0 representing where there were no values for either MCE, 1 representing the values from the weighted MCE only, 2 representing the values from the equally weighted MCE only, and 3 representing the values shared between the two.  

 

Parks Analysis

There are several existing parks within the study area. An analysis was carried out to determine whether the most suitable land in the study area is included within the present park boundaries. The weighted MCE was reclassified for the present and future model, identifying the top ~860 cells as suitable, and the rest of the cells as null.  This involved creating two classes (natural breaks), one at the highest value, and the other ~860 cells below it.  Visually comparing these cells to the outline of the existing park area shows how many of them fall into the park area or outside of it.