Environmental change in Garibaldi Provincial Park, Southern Coast Mountains, British Columbia

Geoscience Canada, Sept, 2004 by Johannes Koch, Brian Menounos, John J. Clague, Gerald D. Osborn

SUMMARY

We are reconstructing Holocene environments in Garibaldi Provincial Park, in the southern Coast Mountains of British Columbia, by examining a diverse set of paleoenvironmental records, including tree-rings, lake sediments, glacial landforms, and photographs. This integrated study, in combination with previous research in adjacent areas, is providing a more detailed picture of past climate, vegetation, and glacier extent in Garibaldi Park than has heretofore been available. The data suggest recurrent, complex, and successively more extensive glacier advances during the last half of the Holocene, followed by dramatic warming, snow and ice loss, and a rise in treeline in the twentieth century. The multi-proxy approach used in this study is broadly applicable to other mountain areas. It yields more reliable and robust paleoenvironmental reconstructions than approaches based on only one or two types of data.

RESUME

Nous travaillons a reconstituer les conditions environnementales holocenes dans le parc provincial Garibaldi, dans la region sud des montagnes cotieres de la Colombie-Britannique, en etudiant divers ensembles de variables representatives du paleoenvironnement, dont les anneaux de croissance des arbres, les sediments lacustres, les formes des paysages glaciaires, et des photographies. La presente etude synoptique, combinee aux resultats des recherches sur des regions adjacentes, nous fournit une image plus detaillee du climat, de la vegetation et de l'etendue glaciaire d'alors dans le parc Garibaldi. Les donnees permettent de penser que durant la derniere moitie de l'Holocene, les avancees glaciaires ont ete recurrentes, complexes et de plus en plus etendues. Par la suite, il y a eu rechauffement spectaculaire, deperdition de neige et glace, ainsi qu'une elevation de latitude de la limite forestiere au cours du XXe seicle. L'approche par combinaisons de variables representatives utilisees dans la presente recherche peut etre employee tel quel pour l'etude d'autres regions montagneuses. Les reconstitutions paleo-environnementales sont plus fiables et plus sures que celles reposant sur un ou deux types de donnees.

INTRODUCTION

The Kyoto Accord and recent droughts on the Canadian Prairies have heightened public interest in climate change. In many areas of the Northern Hemisphere, the 1990s were the warmest decade of the last century and, possibly, the last 1000 years (Fig. 1; Mann et al., 1998). Most climate scientists agree that this recent warming is anomalous, but debate continues about its source. Part of the difficulty in establishing the cause of warming on such short time scales is that Earth's climate system is complex, strongly nonlinear, and behaves in poorly understood ways. One way to improve our understanding of Earth's climate is to study its behaviour over long periods, ranging from centuries to millennia or more (Bradley and Jones, 1993).

[FIGURE 1 OMITTED]

Many biological and physical systems are sensitive to changes in temperature, precipitation, and other climate variables. Their careful study may provide a long-term perspective on climate change and its causes. Confidence in such proxies as faithful recorders of past climate is increased when a common climate signal can be obtained from several independent sources (Mann, 2002).

Alpine and subalpine environments are particularly sensitive to climate change. Many ecological and geomorphic processes in high mountains are influenced by changes in precipitation and temperature (Ryder, 1998; Luckman and Kavanagh, 2000). We are using a multi-proxy approach to reconstruct past precipitation and temperature in Garibaldi Provincial Park in the southern Coast Mountains north of Vancouver over the past several millennia. Garibaldi Park is an ideal location for this research because 60% of the area is above treeline, 21% is covered by snow and glacier ice, and its climate is controlled by both maritime and continental air masses. In addition, Garibaldi Park is near a major urban centre and is one of the most visited provincial parks in British Columbia.

In this paper, we briefly discuss previous paleoenvironmental research in the mountains of western Canada and present some of our findings from Garibaldi Park. The objectives of the paper are to 1) illustrate the main methods used in Holocene alpine environmental reconstruction in the Cordillera of western Canada, 2) show the power of multidisciplinary research in elucidating past enviromnents, and 3) summarize the history of late Holocene environmental change in the park.

Our research is partly driven by the premise that a better understanding of past climate change is important for forecasting future impacts of a warming climate. As glaciers in the southern Coast Mountains recede and, in some cases, disappear, the timing and magnitude of runoff may change significantly, affecting fish populations, power generation, and water supply. The disappearance of glaciers may also impact tourism as they are a major attraction for outdoor enthusiasts. Furthermore, changes in treeline can adversely impact some plants and wildlife that depend on open parkland.