Introduction

For this project I will use a "CostGrow" and "pathway" module to determine the least-cost pathway between greenspaces, railway lines and electricity right-of-ways for a potential wildlife corridor in Burnaby, British Columbia.The Institute of Urban Ecology has been working on creating wildlife corridors in the GVRD for over ten years through their Green Links project, so I thought that it would be interesting to do something GIS-related with regards to this project.


What is Green Links?

Backyard Enhancement Project
The Green Links project was established in 1996 by the Insitute of Urban Ecology.  The goal of the Green Links project is to create wildlife corridors in the GVRD by connecting existing parks, utility right-of-ways, lakes, enhanced backyard habitat and other sensitive ecosystems and green spaces to maintain biodiversity. Although it is widely recognized that habitat size and structure is the most significant factor influencing differences in species richness, this does not mean that small habitat patches in uran environments have no value.  Small habitats in urban areas do have value, and their value increases as patches "are connected through wildlife corridors such as enhanced backyard habitat, utility rights-of-ways, riparian zones, boulevards and road right of ways." (Greater Vancouver Regional District, 2004)

In order to make these linkages, the Institute of Urban Ecology employs several strategies They rehabilitate streams, work with the municipalities to do plantings in parks, clean up ravines and other sensitive ecosystems, and encourage backyard enhancement projects on privatly-owned land. The Institute of Urban Ecology is currently working on three links in the GVRD:

The Coquitlam Link

• Based upon the BC/Gas Hydro Utility corridor running North-South form the BC Hydro Relay satation in the Port Moody Ecological Reseve, through Coquitlam`s city centre and south to the Coquitlam and Fraser Rivers
• Wildlife habitats contiguous to the Coquitlam corridor include: 1)  Colony Farm, 2) The Riverview hospital arboretum, 3)Mundy Park, 4) Mundy Creek, 5) Port Moody Ecological Reserve (Institute of Urban Ecology, 2004)
  

The Delta-Surrey Link

• based upon the BC Gas/BC Hydro utility corridor that runs along the northern edge of Burns Bog, continues east through North Delta and into North Surrey, through Green Timbers and Tynehead Regional Park
• Wildlife habitats contiguous to the proposes Delta-Surrey corridor include: 1) Burns Bog, 2) Low lands Stream, 3)Mahood Creek, 4) Green Timbers, 5) Tynhead Regional Park.  (Institute of Urban Ecology, 2004)
  

The Burnaby Link

• The Southern and Eastern Edge of the Burnaby Link would roughly follow the route of a planned urban trail network starting at Stoney Creek and continuing southwest: past Burnaby Lake Park, Robert Burnaby Park, Byrne Creek Ravine Park and on to the Fraser River.  Although this pipeline corridor does not have a contiguous easement running through the whole area, the Municipality of Burnaby has indicated several Green spaces that have excellent potential for bridging these gaps.  There is also a BC Hydro corridor running from Robert Burnaby Park to the North end of Byrne Creek Ravine Park that would provide another excellent linkage opportunity.
• Wildlfe Habitat contiguous to the proposed Burnaby corridor include: 1) Burnaby Mountain, 2) Burnaby Lake Regional Park, 3) Stoney Creek, 4) Brunette River, 5)Robert Burnaby Park, 6) Deer Lake, 7) Middlegate, 8) Byrne Creek Ravine, 9) Fraser River Park. (Institute of Urban Ecology, 2004)
  

The Methodology and Rationale Behind the Project

Methodology
When I decided to take-on this project , I took it upon myself to contact a staff member at the Institute of Urban Ecology to ask them what type of GIS analysis they would be interested in. I wanted to do something practical and was shocked to learn that they had no GIS data nor had they had any GIS analsyis completed in the past. 

I recieved the following recommendations for an analysis:

1. Urban Gradient Analysis:  This would entail an assessment of the land cover adjacent to the Right-of-ways.
2. Connectivity Analysis: This would entail a) structural connectivity or physical connections using Euclidean distance, and b) Functional connectivity using least-cost distance

Due to a lack of data, more specifically, high resolution vegetation coverage, I opted for doing a simplified version of a structural connectivity analysis.  Instead of using Euclidian distance, I decided to use a "CostGrow" module with a friction surface and a "Pathway" module.  This would enable me to find the least-cost pathway from a point of destination to a centre of origin. 

When using a a friction surface with a cost grow module,  you must indicate the friction for each pixel relative to a base value of 1.  Thus a friction of 2.0 indicates twice the base cost to move through that cell. A friction of 0.5 indicates half the base cost and a -1 friction value represents absolute barriers.  If I did not use a friction surface in my analysis, every cell would be given an identical friction of 1 and the result would be a distance image with values equal to the number of cells from the centre of origin.  (Idrisi Help, 2004)

The "Pathway" module determines the least cost route between one or more target cells and one or more lower terminal cells on an accumulated cost surface. The lowest points on this surface represent the terminal points for the PATHWAY module. Working with the distance or cost distance surface, PATHWAY determines the least-cost route linking the terminal cell and target cell. The image produced is Boolean with the least cost path indicated by ones on a background of zeros. (Idrisi Help, 2004)

Backyard Enhancement Project
Rationale
A structural connectivity analysis would be useful to the Institute of Urban Ecology to determine the least-cost distances between green spaces for several different reasons.  Firstly, most of the land that would be considered for the Green Links is on private land.  A lot of the connections in urban areas will be reliant on private individuals participating by either creating a backyard enhancement project or donating a piece of land in trust.  So, with this in mind, it is more efficient to find the least cost distance between spaces to ensure the success of the project.  Less people to convince means more success for the project.  The Institute would also be more likely to get more support for the project if it was deemed as not infringing on "development."  Secondly, it is more financially feasible for the Insitute to focus on the least-cost pathways since its a non-profit organization relying on unstable or limited funding.



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