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Notes:
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One of the most widespread approaches for setting spatially-explicit priorities for connectivity conservation consists in evaluating the effects of the individual removal of each habitat patch (one at a time) from the landscape. It however remains unknown the degree to which such priorities are valid and reliable in the longer term, as subsequent habitat losses and other disruptions accumulate in the landscape. We compared the patch prioritizations and estimated connectivity losses resulting from individual patch removals and from a more exhaustive assessment accounting for the potentially synergistic impacts of multiple habitat losses by testing all possible combinations of patch removals. Habitat availability (reachability) metrics and metapopulation capacity were calculated in purposefully simulated landscapes and in habitat distribution data for three bird species (NE Spain). We found that 1) individual patch removals allowed identifying areas of low contribution to connectivity that remained so after subsequent network modifications, 2) the most important patches identified through individual removals often did not coincide with those patches whose removal would actually be most detrimental after multiple habitat losses. However, these differences were smaller for the habitat reachability metrics, as well as for very mobile species that were largely insensitive to habitat spatial arrangement. If many patch losses over time are likely, it might be a more robust and fruitful conservation strategy for managers to pinpoint those patches that, with a low negative impact on connectivity, can be converted to other land uses, instead of trying to elucidate through individual patch removals which subset of protected patches would be the most effective for conserving as much connectivity as possible in the long term. Individual patch removals provide useful but non-permanent guidelines that may need to be reassessed when substantial landscape modifications occur, which requires dynamic strategies for connectivity conservation in the face of global change.
Support was provided by the Spanish Ministry
of Science and Innovation through grants AGL2009 – 07140
(DECOFOR), PR2010-0226, AGL2012 – 31099 (GEFOUR), and
CSD2008-00040 (CONSOLIDER-MONTES), and is a contribution
to the FP7-226852 EU-project SCALES. LR benefi ted
from a predoctoral research grant FI from the AGAUR, and a grant
to develop a research stay at the Stockholm Resilience Centre with
the support of the UdL. Ö B received support from Mistra through
a core grant at the Stockholm Resilience Centre and from the Strategic
Research Programme EkoKlim at Stockholm Univ. |
