[PCA] ARTICLES: Interacting Effects of wildfire & drought in a changing environment

[De Angelis, Patricia]

Two recent articles on the interactions between wildfire and climate change
(published in Proceedings of the National Academy of Sciences):

Schoennagel *et al*. 2017. Adapt to more wildfire in western North American
forests as climate changes. PNAS. (early edition).
http://www.pnas.org/content/early/2017/04/11/1617464114.abstract

ABSTRACT:
Wildfires across western North America have increased in number and size
over the past three decades, and this trend will continue in response to
further warming. As a consequence, the wildland–urban interface is
projected to experience substantially higher risk of climate-driven fires
in the coming decades. Although many plants, animals, and ecosystem
services benefit from fire, it is unknown how ecosystems will respond to
increased burning and warming. Policy and management have focused primarily
on specified resilience approaches aimed at resistance to wildfire and
restoration of areas burned by wildfire through fire suppression and fuels
management. These strategies are inadequate to address a new era of western
wildfires. In contrast, policies that promote adaptive resilience to
wildfire, by which people and ecosystems adjust and reorganize in response
to changing fire regimes to reduce future vulnerability, are needed. Key
aspects of an adaptive resilience approach are (i) recognizing that fuels
reduction cannot alter regional wildfire trends; (ii) targeting fuels
reduction to increase adaptation by some ecosystems and residential
communities to more frequent fire; (iii) actively managing more wild and
prescribed fires with a range of severities; and (iv) incentivizing and
planning residential development to withstand inevitable wildfire. These
strategies represent a shift in policy and management from restoring
ecosystems based on historical baselines to adapting to changing fire
regimes and from unsustainable defense of the wildland–urban interface to
developing fire-adapted communities. We propose an approach that accepts
wildfire as an inevitable catalyst of change and that promotes adaptive
responses by ecosystems and residential communities to more warming and
wildfire.


Slingsby *et al*. 2017.  Intensifying postfire weather and biological
invasion drive species loss in a Mediterranean-type biodiversity hotspot.
PNAS. (early edition).
http://www.pnas.org/content/early/2017/04/11/1619014114.abstract

ABSTRACT:
Prolonged periods of extreme heat or drought in the first year after fire
affect the resilience and diversity of fire-dependent ecosystems by
inhibiting seed germination or increasing mortality of seedlings and
resprouting individuals. This interaction between weather and fire is of
growing concern as climate changes, particularly in systems subject to
stand-replacing crown fires, such as most Mediterranean-type ecosystems. We
examined the longest running set of permanent vegetation plots in the
Fynbos of South Africa (44 y), finding a significant decline in the
diversity of plots driven by increasingly severe postfire summer weather
events (number of consecutive days with high temperatures and no rain) and
legacy effects of historical woody alien plant densities 30 y after
clearing. Species that resprout after fire and/or have graminoid or herb
growth forms were particularly affected by postfire weather, whereas all
species were sensitive to invasive plants. Observed differences in the
response of functional types to extreme postfire weather could drive major
shifts in ecosystem structure and function such as altered fire behavior,
hydrology, and carbon storage. An estimated 0.5 °C increase in maximum
temperature tolerance of the species sets unique to each survey further
suggests selection for species adapted to hotter conditions. Taken
together, our results show climate change impacts on biodiversity in the
hyperdiverse Cape Floristic Region and demonstrate an important interaction
between extreme weather and disturbance by fire that may make flammable
ecosystems particularly sensitive to climate change.
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