In 2004, of the 483,610 square kilometers that comprise the Yukon Territory, less than 2% was deemed suitable for agricultural land by the Government of Yukon, Department of Energy, Mines and Resources, Agricultural Branch. The limitations they highlight are geography, climate, and soils. Soils and geography are more fixed over long time scales, but climate is currently shifting.

Within this context I decided to use geographic information systems (GIS), specifically ArcGIS, to re-examine the restrictions on Yukon agriculture, assuming static limitations on soils and geography but a changing climate. My target climate variable was effective growing degree days (EGDD) as a measure of suitability for crops, both in the soil and in greenhouses. As temperature increases, so does the number of EGDDs, and my project focuses on this trend.

Background

Spark for my project:

I spent my past summer in the Yukon, which is a place of powerful, breathtaking nature. The summers are short and fantastic, the winters (I've heard) are cold and dark. I was a research assistant in the Kluane area, which is subject to daily afternoon winds that pick up and distribute loess (extremely fine glacially eroded material) all over the local area (the image to the right shows the beginning of one of these "loess storms"). The “organic” soil layer is visibly speckled by particles of loess. I found this interesting, as I know that loess is nutrient rich and can be very good for agriculture. Abbotsford, near Vancouver, BC, is an outwash plain covered by layers of loess, is called a hub for agribusiness, and is considered to have excellent soils. Integrating this knowledge, I became interested in what sort of limitations related to temperature would be lifted by climate change. It was fascinating to me to think that amidst all the worry surrounding climate change and the negative scenarios that arise, there would of course be other areas that have the potential to benefit substantially.  I don't believe, and the literature seems to agree, that temperature alone is enough to entirely lift the limitations for agriculture, as water, soils, and access are still issues. Given this, however, I wanted to perform an analysis which accounted for the less responsive land variables of water, soils, and roads, while varying the key factor affected by temperature: growing degree days.

Growing Degree Days:

Growing Degree Days (GDD) are a common agricultural measure of growing season length, which is key for longer growing crops such as wheat and other grains (source). They are essentially a measure of heat accumulation throughout the year, based on a threshold “base” temperature. I will explain the specific calculations in greater detail in the methods section, but the basic idea is that more GDD = longer growing season, and higher temperatures = more GDD = longer growing season. There are specific classes associated with GDDs that correspond to kinds of crops that can be grown, and these are summarized here:

Class 1        1400-1600 GDD

These lands have no significant limitations that restrict the production of the full range of common Canadian agricultural crops (none in Yukon).

Class 2        1200-1400 GDD

These lands have slight limitations that restrict the range of some crops but still allow the production of grain and warm season vegetables (none in Yukon, based on a 30 year average).

Class 3        1050-1200 GDD

These lands have moderate limitations that restrict the range of crops to small grain cereals and vegetables (in a few localized areas in Yukon).

Class 4         900-1050 GDD

These lands have severe limitations that restrict the range of crops to forage production, marginal grain production and cold-hardy vegetables (valleys of central Yukon).

Class 5         700-900 GDD

These lands have very severe limitations that restrict the range of crops to forages, improved pastures and cold-hardy vegetables (the most common class of agricultural land in Yukon).

Class 6        <700 GDD

These lands have such severe limitations for cultivated agriculture that cropping is not feasible. These lands may be suitable for native grazing.

Class 7

These lands have no capability for cultivated agriculture or range for domestic animals.

 
(data from the Yukon Agriculture Branch Quarterly Bulletin, Winter 2003)

Other Criteria:

 Soils

Soils are quite important for any agriculture that occurs in the ground. Yukon soils are generally deficient in nitrogen and phosphorous, key nutrients for plants, and permafrost is discontinuously spread over the territory. Drainage is also key, as it will be an indication of moisture content. Given the time frame of my project, I chose to focus only on texture, which is a proxy for both drainage and nutrients. Loam is highly desired for agricultural as it is nutrient rich and retains water without holding it too tightly for plants to draw on. Clay can be good in a dry environment if it retains water, but can hold water too tightly for plants to draw on. Sand drains quite quickly, and is therefore less advantageous in a dry environment. These different qualities will have implications for the classification scheme I use in my analysis.

 Water

 There are two main climate factors that are limiting in the Yukon: it's cold and it's dry. With higher temperatures, the effective growing degree days will increase, allowing the growth of crops that require longer seasons, and allowing agriculture to take better advantage of the extended daily sunshine in the North. The primary limitation of climate, then, will become precipitation and/or access to water. Based on a map of predicted 2050 precipitation, the Yukon is not expected to see much of a change, positive or negative, in precipitation. Because of this limitation I've weighted proximity to rivers  fairly heavily as part of the restriction on potential agricultural land (more on this in the methods section). This doesn't necessarily solve the problem of water limitation, as the rivers can only support so many people, but it provides a likely short-term scenario.

Slope

Slope is important from an engineering perspective, as a field on a 30% slope would be rather difficult to maintain, and areas with steep slopes are often more heterogenous topographically, with gullies and ridges affecting the microclimate of vegetation and soils. Thus, I characterized slopes based on my own knowledge (from geomorphology classes) of the processes and stability of varying degrees of slope.

A note on Ecodistricts:

My GDD and temperature data is assigned to polygons called ecodistricts. From NRCAN:

            “Each EcoDistrict is characterized by relatively homogeneous biophysical and climatic conditions. The differentiating characteristics of EcoDistricts are: regional landform, local surface form, permafrost distribution, soil development, textural group, vegetation cover/land use classes,range of annual precipitation, and mean temperature.”