34 Haida Gwaii Is an Archipelago of More Than 200 Islands Located Be
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4 THE ENVIRONMENT OF HAIDA GWAII 4.1 About the Islands Haida Gwaii is an archipelago of more than 200 islands located be- tween Vancouver Island and southeast Alaska, 50–30 km off the north- ern mainland coast of British Columbia (Figure .). The archipelago is scimitar shaped, and extends 250 km from north to south. Together, Graham and Moresby Islands constitute 90% of the nearly million hectares that comprise the archipelago. These two main islands are nar- rowly separated by Skidegate Inlet and Skidegate Channel. Other large islands in the archipelago include Louise, Lyell, and Burnaby Islands off the east coast of Moresby Island, and Kunghit Island to the south of Moresby Island. The landscape of the islands is extremely varied: it ranges from broad sand beaches and dunes on the east coast to the rocky, surf-battered west coast, and from muskeg lowlands on Graham Island to the rug- ged, strongly eroded Queen Charlotte Ranges of Moresby Island. The prevailing tranquil environment of Haida Gwaii is at times interrupted by dramatic natural processes—fierce storms, high-energy surf, floods, landslides, earthquakes, and windthrow—events that substantially modify the landscape and the ecosystems of the islands. In many ways, the archipelago is a microcosm of coastal British Columbia, but it has its own distinctive, and in some respects unique, natural and cultural heritage. The lands and waters of Haida Gwaii support a rich cultural heritage. Archaeological evidence indicates continuous human presence by the Haida and their ancestors dating back 0 000–3 000 years. Today, seven main communities are located on the east and north coasts of Graham Island and on the northeast tip of Moresby Island. Tourism, forestry, and fishing are the main economic drivers. About 4500 people of varied ancestry, almost half of them Haida, currently live on Haida Gwaii. Approximately 52% of Haida Gwaii’s land base is currently within pro- tected areas, including heritage sites and conservancies, Gwaii Haanas National Park Reserve and Haida Heritage Site, Naikoon Provincial Park, and the Vladimir J. Krajina Ecological Reserve. 34 Haida Gwaii Field Guide 4.2 Climate6 Haida Gwaii’s climate is driven by the archipelago’s proximity to the Pacific Ocean (all of the archipelago lies within 40 km of tidewater), its separation from the continent, and the combination of physiography and movement of moist air masses off the Pacific Ocean. The ocean moderates air temperatures on the islands throughout the year. Moreo- ver, the mainland Coast Mountains and Hecate Strait provide protec- tion and separation from cold winter and hot summer continental air masses, which only rarely reach the islands. The prevailing flow of the jet stream from the open Pacific Ocean toward the east is responsible for most of the air masses that move over Haida Gwaii. Throughout the late spring and summer (mid May to mid September), the North Pacific High Pressure System creates relatively dry, occasionally sunny conditions over the islands. As the North Pacific High begins moving south in September, it is replaced by the Aleutian Low, which engenders the cloudy skies, heavy precipitation, and strong winds that are typical during autumn and winter. These conditions create a cool temperate, humid to perhumid, oceanic type of climate. The mean annual temperature of tidewater stations is 7–8°C, and the ranges in daily, seasonal, and annual air temperature are all narrow. Fall and early winter are mild and very wet. Winter is cool but rarely cold, and rainy, with more snow at higher elevations. Snowpack along the coast is usually ephemeral, but more snow falls at 6 This discussion draws on data that were summarized for the reference period 1961–1990 (Table 5.2) and which were generated using Climate WNA (www. genetics.forestry.ubc.ca/cfcg/ClimateWNA/ClimateWNA.html), except for 1961–1990 temperature or precipitation normals from specific stations, which were acquired from Environment Canada records (http://climate.weather.gc.ca/ [2013]), particularly mean annual precipitation values referenced in Section 4.2.2. ClimateWNA extracts and downscales PRISM monthly data (Daly et al. 2002) and calculates seasonal and annual climate variables for specific locations based on latitude, longitude, and elevation. Initial development of the PRISM climate surfaces incorporated point data from climate stations, including stations on Haida Gwaii (Cape St. James, Sandspit, Tlell, Sewell Inlet, Tasu Sound, Masset CFS, Masset, Port Clements, Sewall Masset Inlet, and Langara). All stations are located in the CWHvh3 or CWHwh1 low-elevation variants. See Chapter 5 and Table 5.2 for summaries of climate in relation to biogeoclimatic units of Haida Gwaii. Haida Gwaii Field Guide 35 higher elevations (especially above 600 m) and in the interior of the larger islands. Summer is cool and moist but with periodic warm, dry spells, especially on the leeward east coast. Summer cloud cover is very common, and fog occurs frequently. 4.2. Temperature Mean annual temperature is fairly consistent at lower elevations due to the moderating effect of the ocean. It averages 7–8°C at low elevations everywhere, and declines with increasing elevation. Estimated mean annual temperature is slightly higher than 6°C for montane areas and slightly lower than 6°C for the subalpine. Degree-days are the cumulative annual total of Celsius degrees that the mean daily temperature is above or below a certain threshold. Two common thresholds used are growing degree-days (>5ºC) and chill- ing degree-days (<0ºC). The average number of growing degree-days is greatest at low elevations throughout Haida Gwaii (i.e., 340–400), and declines to 62 in montane areas and 066 in the subalpine. The number of chilling degree-days is lowest at lower elevations (about 64) and increases with elevation (>230 for montane and >260 for subalpine areas). The frost-free period ranges from about 00 days in northern, higher elevations to more than 300 days at Cape St. James, which has one of the longest known frost-free periods in Canada (Williams 968). Although the frost-free period and growing season on Haida Gwaii are long, the number of growing degree-days is low compared to southern and less oceanic parts of the British Columbia coast. Thus, the number of effective growing degree-days (Coligado 98) is relatively even lower. 4.2.2 Precipitation The Queen Charlotte Mountains cast a rain shadow on eastern Graham and Moresby Islands, which results in a decrease in annual precipitation from more than 3000 mm on some of the low-elevation windward slopes to <500 mm on the eastern lowlands. Mean annual precipitation (MAP) from the east to the west side of the islands ranges from 042 mm to 7445 mm (see Table 5.2). The orographic effect of the Queen Charlotte Mountains creates a large disparity in precipitation between windward and leeward sides of the islands. The mountains force the wet air that moves in from the Pacific 36 Haida Gwaii Field Guide Ocean to rise, cool, and deposit moisture as rain or snow on the western slopes. Most of the eastern, leeward side of the islands is in a moderate rain shadow. Where there are breaks in the mountain barrier, such as Skidegate Channel and the low pass between Newcombe and Sewell Inlets, moist air can penetrate and intensify precipitation at eastern localities. The northern and southern tips of the archipelago (Langara Island and Cape St. James) are scarcely influenced by orographic lift- ing or rain shadow effects; therefore, the amount of precipitation they receive is intermediate between the windward west (e.g., Tasu Sound) and leeward east (e.g., Tlell) sides of the archipelago. Eastern Haida Gwaii is the driest region of the islands. Tlell and Sand- spit have MAP of 26 mm and 359 mm, respectively (Environment Canada 2037), and represent the drier, rain shadow extreme of eastern Haida Gwaii. The west side is much wetter, withMAP in excess of 3000 mm. There are two active weather stations in wetter (windward) areas— on Langara Island in the north and Cape St. James in the south—which report 874 mm and 542 mm MAP, respectively (Environment Canada 203). However, neither station is influenced by the orographic effects that prevail throughout most of western Haida Gwaii. The Tasu weather station, with a west coast location strongly affected by orographic lift- ing, recorded MAP of 428 mm over the period 95–980. MAP gener- ally increases with elevation. In montane areas, MAP is >2500 mm; in the subalpine, it is more than 4000 mm. Precipitation strongly influences the distribution of biogeoclimatic units (see Chapter 5). There are also strong seasonal differences in precipitation. Summer weather and climate are dominated by the North Pacific High, which results in northwesterly winds and less precipitation, compared with other seasons. Mean precipitation in the driest month (July) is only about 20% of that in the wettest month (October). The Aleutian Low dominates the winter weather and brings frequent strong southeasterly winds and heavy rains. The orographic effect is thus most pronounced during the wettest months. Very little snow falls at coastal localities on Haida Gwaii, and it usu- ally melts within a few days. Mean annual snowfall at lower elevations 7 Climate normals for 1961–1990 were acquired from http://climate.weather.gc.ca/ Haida Gwaii Field Guide 37 ranges from 52 cm on the east side to 260 cm in wetter (west side) areas. Snowfall in the interior of the islands and at higher elevations is estimated at more than 300 cm annually for montane areas and more than 600 cm for the subalpine. Williams (968) estimated that at eleva- tions of 300–600 m, snowfall of 00–20 cm per month could occur in some winters, and the resulting snowpack would be deep and long lasting.