[Editor's note: Today the Tyee published what may be the first ever interactive carbon map of British Columbia. See the introductory story here. This story shows where the data came from and how it was used in the map.]
Where does B.C. leave its deepest climate footprint? Where do natural processes "clean up" some of our greenhouse emissions for us? The Interactive B.C. Carbon map is a first-of-its-kind Tyee Solutions Society contribution to helping all British Columbians visualize our greenhouse-gas balance at-a-glance.
The map identifies and locates specific activities within B.C.'s borders that are having the greatest impact on our future climate, as "sources" or "sinks" of atmospheric carbon. The colour scale indicates the relative potency of such factors as highways (pink "sources") and coastal eelgrass beds (green "sinks"). The associated table displays an estimate of how much carbon is captured or released over a year by the human and natural activities mapped in the visible window.
Behind both the table and visualization is an enormous amount of underlying data -- everything from traffic counts on individual sections of provincial highway to the location of the densest patches of coastal marine vegetation. Where did all that information come from? And what assumptions and compromises were we forced to make in bringing it all together?
We thought you might ask, so here we go:
BC CARBON EMISSIONS
The primary source for our emissions data was the British Columbia government, as follows:
Big industrial facilities
Industrial facilities with emissions greater than 10,000 tonnes of CO2 equivalent (tCO2e) -- responsible for about 30 per cent of total B.C. emissions -- were identified for the first time by the B.C. provincial government in 2010.
In that report, individual facilities reporting less than 10,000 tCO2e are aggregated, by company, as "Linear Facilities." Locations are not provided. As such, we did not include them in our map or map-based calculations. Those facilities collectively emit approximately 2.9 million tCO2e per year, meaning that total facility emissions of GHGs in B.C. are in fact about 20 per cent higher than they appear here.
An estimated 45 per cent of British Columbia's greenhouse gas emissions are under the jurisdiction of municipal governments or arise from their operation of everything from community centres to road maintenance equipment.
These governments provide Community Energy and Emissions Inventory Reports (CEEI) that estimate energy use and GHG emission for three primary sectors -- buildings, on-road transportation and solid waste -- and further provide "supporting indicators" for housing type, residential density, commuting distances and green space.
CEEI reports include emissions from on-road transportation through communities. But we also referred to other sources for emissions from traffic (see below: Transportation Emissions). To avoid double counting, we reduced community emission totals by the amount of emissions reported for all roads passing through those communities (up to the total amount of transportation-related emissions the community had reported).
CEEI reports also include data on large industrial facilities, but that data is described as a "memo item" and not included in the reported community emissions totals. As such we did not need to adjust the CEEI values to avoid double-counting of facilities emissions.
The CEEI covers a variety of jurisdictions, including cities, villages, regional municipalities and district municipalities. We left two kinds of jurisdictions off our map. Those are "District Municipalities" and "Regional District Unincorporated Areas." These very large, rural areas cover 99 per cent of the map of B.C., but according to the CEEI produce only 12 per cent of community carbon emissions. When we subtracted vehicle emissions (already represented in traffic data) from the GHGs these areas are responsible for, their portion of all community-generated carbon drops to five per cent.
Had we displayed these large jurisdictions meanwhile, their extent would have obscured most other features of our visualization. For the sake of legibility then, we opted to leave them out. As a consequence, however, their emissions aren't included in our map-based emissions table, whose emissions value for "communities" is therefore approximately five per cent lower than it should be.
We also used the most recent CEEI reports that were available to us when we were building the map. Those date to 2007. During our work, the B.C. Ministry of Environment let pass several stated target dates for the release of updated data from 2010. Draft data were released late in June, but would not be finalized until September and were thus not available in time to include in this version of the visualization.
Transportation Emissions by Highway/Road
Roads and highways on the map have been colour coded based on traffic emissions -- the darker the red, the higher the emission -- based on data from the B.C. Ministry of Transport and Infrastructure's Annual Traffic Volumes 2004-2010. The MoT divides the provincial highway network into segments. Traffic data is collected for each of these segments continuously at roadside count sites. We used "annual average daily traffic" (AADT) data, representing an average of the number of vehicles travelling past a given count site each day over a year, collected over the years 2006-2011.
For each road segment we used data from the most recent year available. In a few cases (about four per cent of the total) no data had been recorded after 2005. We excluded those segments from our calculations (explaining some of the blanks on our visualization).
To calculate highway emissions from these traffic data, we also needed to find out the following:
- The average fuel consumption of cars, light trucks, medium trucks, freight light and freight heavy trucks. We got this from federal Natural Resources Canada data provided by B.C. Ministry of Environment.
- Some measure of the ratio of diesel to gasoline burning vehicles on the road (each release different amounts of emissions). We referenced the data tables on pages 2 and 3 of the CEEI report for British Columbia.
- A formula for translating fuel consumption into CO2 emissions. Here again we turned to NRCan data provided by the B.C. Ministry of Environment.
Using the foregoing, we calculated a provincial average vehicle emission value of 298 grams of CO2e per kilometre driven. That was arrived at by weighting the fuel efficiency values of various vehicle types (cars, light trucks, heavy trucks, etc) according to the proportion of each vehicle type on the road, the types of fuel they use (gasoline versus diesel) and the average distance that those vehicle types are driven each year in B.C. Most of these data came from province-wide summaries provided by the Ministry of Environment. The exception was the proportion of diesel-to-gasoline fuel use per vehicle type; this, as indicated above, came from the Community Energy and Emissions Inventory (CEEI), and necessarily included only communities participating in that survey. In some cases we had to assume the equivalency of differently named vehicle categories between data sources; for example, "commercial vehicle" was assumed to be essentially the same as "light and medium trucks."
From our calculated provincial average vehicle emission of 298 grams of CO2e per kilometre driven, we estimated emissions for each reported highway segment (traffic, times average emissions/kilometre, times length of the segment in kilometres).
The carbon densities calculated for each road segment were thus based on our single province-wide weighted average fuel efficiency. That means that in stretches of road where cars tend to get lower or higher than average mileage, because of local driving conditions, our estimates will be correspondingly inaccurate. As an example, the stretch of Highway 91 that displays our highest estimated carbon footprint density is notoriously slow-going during rush hour; vehicle fuel efficiencies are likely much lower than average there, and actual carbon emissions accordingly higher than our visualization shows.
BC CARBON SINKS
We are grateful to the British Columbia Marine Conservation Analysis, a collaborative project to identify areas of high conservation or human-use values on Canada's Pacific coast, for permission to use its eelgrass mapping data. These data compile the best available information from a variety of sources including the Community Mapping Network, Fisheries and Oceans Canada, the Living Oceans Society, Parks Canada and the Province of British Columbia.
Sierra Club marine specialist Colin Campbell provided coefficients to translate organic carbon sequestration by eelgrass and salt marshes to grams of atmospheric CO2 (1gm Carbon = 3.67gm CO2). Campbell is the author of a report on B.C. eelgrass that concluded that B.C. eelgrass and salt marshes sequester more than 180,000 tonnes of C02e/year. (See page 2 of that report.)
Salt marsh distribution was based on data from the B.C. Shorezone Mapping system, provided to us by the Ministry of Forest Lands and Natural Resource Operations. The Shorezone inventory was developed primarily by reviewing video recordings taken during helicopter and fixed-wing overflights of the entirety of the B.C. coastline. The flights were principally conducted in 1995. The locations of species associated with salt marsh were drawn from the dataset. The choice of species followed the Washington State Shorezone approach to salt marsh identification. However, the only species associated with salt marsh and present in significant amounts in Canada is Salicornia. The shorezone database includes areas and also linear bands denoting species presence; in the case of bands, the recorded widths were used to reconstruct their areas.
The Canadian Forest Service provided estimates of forest carbon intensity by "ecozones" (based on work described in "An inventory-based analysis of Canada's managed forest carbon dynamics, 1990 to 2008," by Stinson et al, 2011.)
The Canadian Forest Service provided us with several alternative measures of carbon intensity for each ecozone. We chose "net ecosystem exchange" -- an inclusive measure of the sequestration and emission of carbon from all forest-related processes.
However the spatial scale of an ecozone constituted a significant limitation. These are extremely large areas, often reaching beyond B.C.'s borders. We learned that new data was currently being prepared at the much more granular level of management units (timber supply area and tree farm licenses) and Biogeoclimatic Ecosystem Classification (BEC) zones; these results were unfortunately not ready to be released. In consequence, and in order to avoid counting carbon being sequestered (or released) in adjacent jurisdictions, we were forced to assume a uniform carbon flux across each ecozone.
To determine B.C.'s share of the carbon flux within trans-border ecozones, we first calculated a carbon exchange value per square kilometre of forest for that ecozone (based on its area of forest and the total net ecosystem exchange value provided to us for that zone). We then isolated the managed forests area within B.C., multiplying that by the average per-kilometre carbon exchange value to produce now, provincial-only totals.
The real carbon that forests sequester or release obviously varies greatly by location and topography within ecozones. Necessarily having to treat these vast landscapes as uniform in the absence of more refined spatial data will have introduced inevitable errors to our visualization, especially in zoomed-in views. We find this gap in public data particularly troubling.
We were also offered forest carbon intensity data by the provincial Ministry of Environment, which included data limited to more recent years than that which we obtained from the CFS. That data was, however, even more spatially imprecise, preventing its accurate use in helping to visualize where B.C.'s emissions and carbon sinks occur.
For a full introduction to the BC interactive carbon map, see this story. Tomorrow: Lessons Learned.
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