Opinion
Urgent preservation of boreal carbon stocks and biodiversity

https://doi.org/10.1016/j.tree.2009.03.019Get rights and content

Containing approximately one-third of all remaining global forests, the boreal ecosystem is a crucial store of carbon and a haven for diverse biological communities. Historically, fire and insects primarily drove the natural dynamics of this biome. However, human-mediated disturbances have increased in these forests during recent years, resulting in extensive forest loss for some regions, whereas others face heavy forest fragmentation or threat of exploitation. Current management practices are not likely to maintain the attendant boreal forest communities, nor are they adequate to mitigate climate change effects. There is an urgent need to preserve existing boreal forests and restore degraded areas if we are to avoid losing this relatively intact biodiversity haven and major global carbon sink.

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.

References (80)

  • R. Latifovic

    Land cover mapping of North and Central America-Global Land Cover 2000

    Remote Sens. Environ.

    (2004)
  • C.J.A. Bradshaw

    Tropical turmoil – a biodiversity tragedy in progress

    Front. Ecol. Evol.

    (2009)
  • G.B. Bonan

    Forests and climate change: forcings, feedbacks, and the climate benefits of forests

    Science

    (2008)
  • I.G. Warkentin et al.

    Financing tropical forest preservation

    Science

    (2008)
  • K.E. Ruckstuhl

    Introduction. The boreal forest and global change

    Proc. R. Soc. Lond. B. Biol. Sci

    (2008)
  • D. Mollicone

    Human role in Russian wild fires

    Nature

    (2006)
  • Q. Zhuang

    CO2 and CH4 exchanges between land ecosystems and the atmosphere in northern high latitudes over the 21st century

    Geophys. Res. Lett.

    (2006)
  • D.M. Olson

    Terrestrial ecoregions of the world: a new map of life on Earth

    Bioscience

    (2001)
  • Achard, F., et al., (2005) Identification of Hot Spot Areas of Forest Cover Changes in Boreal Eurasia (EUR 21684 EN),...
  • FAO (2006) Global Forest Assessment 2005. FAO Forestry Paper 147,...
  • Greenpeace

    Roadmap to Recovery. The World's Last Intact Forest Landscapes

    (2006)
  • T.M. Brooks

    Habitat loss and extinction in the hotspots of biodiversity

    Conserv. Biol.

    (2002)
  • United Nations (2000) Forest Resources of Europe, CIS, North America, Australia, Japan and New Zealand (industrialised...
  • F. Achard

    The effect of climate anomalies and human ignition factor on wildfires in Russian boreal forests

    Philos. Trans. R. Soc. Lond., B

    (2008)
  • F. Mouillot et al.

    Fire history and the global carbon budget: a 1° × 1° fire history reconstruction for the 20th century

    Glob. Change Biol.

    (2005)
  • M. Mönkkönen et al.

    Taxonomic diversity of the terrestrial bird and mammal fauna in temperate and boreal biomes of the Northern Hemisphere

    J. Biogeogr.

    (1997)
  • IPCC (2007) Climate Change 2007: Synthesis Report. Contribution of Working Groups I, II and III to the Fourth...
  • B.B. Stephens

    Weak northern and strong tropical land carbon uptake from vertical profiles of atmospheric CO2

    Science

    (2007)
  • Intergovernmental Panel on Climate Change (2001) Climate Change 2001: The Scientific Basis, Cambridge University...
  • S. Kellomäki

    Sensitivity of managed boreal forests in Finland to climate change, with implications for adaptive management.

    Philos. Trans. R. Soc. Lond., B

    (2008)
  • J.M. Chen

    Boreal ecosystems sequester more carbon in warmer years

    Geophys. Res. Lett.

    (2006)
  • E.S. Euskirchen

    Importance of recent shifts in soil thermal dynamics on growing season length, productivity, and carbon sequestration in terrestrial high-latitude ecosystems

    Glob. Change Biol.

    (2006)
  • R. Hyvönen

    The likely impact of elevated [CO2], nitrogen deposition, increased temperature and management on carbon sequestration in temperate and boreal forest ecosystems: a literature review

    New Phytol.

    (2007)
  • J.G. Canadell

    Contributions to accelerating atmospheric CO2 growth from economic activity, carbon intensity, and efficiency of natural sinks

    Proc. Natl. Acad. Sci. U. S. A.

    (2007)
  • R.A. Houghton

    Mapping Russian forest biomass with data from satellites and forest inventories

    Environ. Res. Lett.

    (2007)
  • C.L. Goodale

    Forest carbon sinks in the northern hemisphere

    Ecol. Appl.

    (2002)
  • J. Fang

    Overestimated biomass carbon pools of the northern mid- and high latitude forests

    Clim. Change

    (2006)
  • B. Bond-Lamberty

    Fire as the dominant driver of central Canadian boreal forest carbon balance

    Nature

    (2007)
  • C. Crevoisier

    Drivers of fire in the boreal forests: data constrained design of a prognostic model of burned area for use in dynamic global vegetation models

    Geophys. Res. Lett.

    (2007)
  • Cited by (0)

    *

    All authors contributed equally to this manuscript.

    View full text