Trends in Ecology & Evolution
OpinionUrgent preservation of boreal carbon stocks and biodiversity
Introduction
Much world attention has focused on the loss and degradation of tropical forests over the last three decades [1]. An expansive reservoir for global biodiversity, these forests also contain substantial stores of terrestrial carbon (C) and have an enormous influence on regional and global climates through evaporative cooling processes and the sequestration of C linked to high primary productivity [2]. Although concern rightly persists over continued exploitation of tropical forests [1], a more global perspective on forest loss is necessary so that growing threats to other ecosystems are not ignored [3]. Constituting about one-third of extant forests on Earth and home to nearly half of the remaining large tracts of intact forest, boreal ecosystems support a diverse flora and fauna and likewise harbour a substantial portion of global C stocks [4].
Human populations are typically sparse in boreal zones so there has been relatively limited resource exploitation in these areas, and disturbance dynamics have been largely driven by natural processes such as fire [5]. Consequently, few regions of the boreal forest have been extensively modified compared with their tropical counterparts [6]. However, rising demand for resources (mineral, energy, timber) has increased the extent of perturbation [7], while fire dynamics have been altered due to human encroachment and climate change [8]. Although less immediately threatened by deforestation than the tropics, these remaining havens of the boreal forest could quickly become as threatened as tropical systems [1] while releasing substantial amounts of C into the atmosphere [9].
Based on our review of data on the changes occurring in boreal forest cover, we propose here that immediate action must be taken to preserve this vital world resource.
Section snippets
A rapidly changing forest
We used the Boreal Forest Monitoring Project's [10] delineation of the region (2000 to 2005) to assess patterns of change over time. They defined the boreal zone based on the Terrestrial Ecoregions map of the World Wildlife Fund [11], with modifications to add ecoregions of temperate coniferous and mixed forests characterized by similar seasonality and presence of winter snow cover. Also included were forested areas of forest-steppe ecoregions within continental North America and Asia and those
Biodiversity threats
There are currently about 20300 species found within the boreal forest zone [4], but tree diversity in this zone is relatively low compared with other temperate forests (e.g. Pacific Rim) 13, 16. For birds and mammals in the boreal forest zone, the lowest diversity at all taxonomic levels occurs in Europe, and the highest in western North America and east Asia [20]. To examine the degree to which boreal species are threatened, we searched the IUCN's 2008 Red List (www.iucnredlist.org) for
Changing patterns of carbon storage and flux
Like its proportional forest coverage, the boreal ecosystem contains roughly 30% of the stored terrestrial C of the Earth, with an estimated 550 Gt C in combined soil and above-ground pools [21]. Although the boreal forest has primarily been considered a long-term global C sink, recent studies suggest that the rate of uptake may not be as high as once thought [22]. Various models additionally predict that the boreal biome is the region most likely to be altered by climate change over the next
Recommendations to manage biodiversity and carbon retention simultaneously
Considering that boreal regions are at latitudes where climate warming will be globally most profound [4], it is our opinion that current practices of boreal forest management (Box 1) are inadequate to deal with the pace and magnitude of expected changes [55]. The essential role of boreal forests in C sequestration itself is strong justification to create large forest reserves [44]. Such large forest reserves are possible in Canadian and Russian boreal forests, and we argue that these countries
Acknowledgements
NSS was supported by a Sarah and Daniel Hardy Visiting Fellowship at Harvard University while this manuscript was prepared. We thank F. Achard (Institute for Environmental Sustainability, Joint Research Centre of the European Commission) and C. Pollock (IUCN Species Programme) for assistance in accessing data.
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All authors contributed equally to this manuscript.