Habitat fragmentation and its lasting impact on Earth’s ecosystems

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Science Advances  20 Mar 2015:
Vol. 1, no. 2, e1500052
DOI: 10.1126/sciadv.1500052

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  • Natural versus anthropogenic fragmentation in the boreal forest
    • Nick M. Haddad, Professor, North Carolina State University
    • Other Contributors:
      • Joseph O. Sexton, Senior Scientist, Global Land Cover Facility

    This entire exchange took place originally on the ALERT conservation website in April, 2015. As part of that exchange, Dr. Corey Bradshaw penned an independent perspective: Missing the Forest Despite its Trees Bradshaw’s perspective emerges from his key work summarizing conservation issues facing boreal forests (Bradshaw, et al. 2009).

    Dr. Wells’ comments regarding the ecological importance of boreal forests are valuable. The boreal forest houses enormous stocks of carbon; it is the origin of many major rivers transporting nutrients to and from the Arctic Ocean; and its trophic system provides essential ecosystem services to human communities. Dr. Wells confirms what is shown in our Figure 1 when pointing out that the boreal forest is one of the greatest remaining expanses of forest on Earth.

    We agree with Dr. Wells’ assertion of the conservation value of boreal forest, and our global forest analysis

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    Competing Interests: None declared.
  • Missing the forest despite its trees
    • Corey Bradshaw, Sir Hubert Wilkins Chair of Climate Change, The University of Adelaide

    Despite its immense size, there is little doubt that the ugly second cousin of forest conservation is the boreal region covering much of Alaska, Canada, Fennoscandia and Russia. Indeed, extending some 1.4 billion hectares, of which well over 60% is found in Russia alone (1, 2), the entirety of the boreal forest is more than double the area of the Amazon forest. Yet despite this massive expanse, the impressive biota it shelters (2), and its important contribution to the global carbon (1), nitrogen (3) and oxygen (4) cycles, the boreal is an oft-overlooked region in terms of global conservation priorities and possibilities (5).

    The exchange between Haddad & Sexton ( and Wells ( regarding the former researchers’ recent paper (6) highlights this problem, of which even many expert ecologists are often only vaguely aware. Wells takes particular issue with Haddad and colleagues’ (6) assertion that the boreal forest is highly fragmented, claiming to the contrary that the (North America) boreal forest is “… truly intact … ”. While Haddad & Sexton respond that they did not differentiate between ‘natural’ and human-caused fragmentation, my view is that the exchange misses some important concerns ab...

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    Competing Interests: None declared.
  • North American Boreal Forest Is One of Largest Intact Primary Forest Areas on Earth Not Highly Fragmented as Paper Suggests

    The paper “Habitat fragmentation and its lasting impact on Earth’s ecosystems” by Nick Haddad and 23 co-authors published in the 20 March, 2015 issue of Science Advances provided an incredibly important documentation of the many and varied negative impacts to biodiversity that result from human-caused large-scale fragmentation of intact forest habitats. Although there are regional differences in the ways in which fragmentation impacts various biodiversity features, the effects are largely generalizable across the world’s forests.

    There are a few regions of the globe where there remains large tracts of forest that are not fragmented by human activities—so-called primary forests. These areas have been mapped in a number of ways over recent decades and all show five large areas of remaining primary forest. The largest are the North American Boreal Forest, the Siberian Boreal Forest, the Amazon Forest followed by the Congo Basin Forest and the forests of New Guinea and other parts of Indonesia. In fact, some analyses indicate that the world’s largest single intact blocks of forest habitat are now found in the Amazon and in Canada’s Boreal Forest.

    Given these facts it was astonishing and disappointing to see in the paper, a map purporting to show forested areas of the globe that are most impacted by fragmentation (defined in the paper as “the division of habitat into smaller and more isolated fragments separated by...

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    Competing Interests: None declared.

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