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Resilience
Key messages:
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Woodland dieback caused by climate change, Adrian
Newton.
Human wellbeing depends on maintaining
ecosystem functions and services in the face of
increasing environmental change. Ecological
resilience is increasingly a policy goal (Box 1),
with a need to apply ecological concepts relating
to resilience to environmental management. Yet
there is discussion about how to define and
measure resilience, with evidence about
resilience strongly lagging behind theory.
Biodiversity and Ecosystem Service
Sustainability (BESS) research is contributing in
three areas:
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Defining resilience
Evidence about declining resilience
Maintaining resilience
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The term resilience has multiple
definitions and encompasses
several different properties of
ecological systems.
Academics, practitioners and
policy makers tend to refer to
resilience in different ways, with
the potential for unintended
biodiversity loss [1].
UK-wide biodiversity loss will lead
to lower resilience of ecosystem
functions to future perturbations [2].
Trait diversity increases resistance
to drought on chalk grasslands.
Measuring and monitoring
resilience is challenging and there
is a need for indicators linked to
the mechanisms underpinning
resilience [3].
Forest resilience can be measured
through the analysis of recovery
trajectories [4].
Connectivity increases the
resilience of temperate forest and
shallow lake ecosystems.
1. Resilience in environmental policy:
What exactly is resilience?
Parties at the 2010 Convention on
Biological Diversity agreed a mission that
includes to ‘to ensure that by 2020
ecosystems are resilient and continue to
provide essential services…’.
Given the multiple pressures on ecosystems and
the need to adapt to environmental change,
aiming for ‘resilient’ landscapes is an appealing
vision. The term resilience has become a
‘boundary object’: a concept with slightly different
uses and interpretations by different communities
[5]
. Boundary objects have benefits of bringing
people together from different disciplines, as long
as there is awareness of the potential for
misunderstanding. Resilience may be used to
refer to particular properties of ecosystems, in a
A 2011 Government White Paper included
commitments to ensure ecological
resilience
Section 6 of The Environment Act (Wales)
places a duty on public authorities to seek
‘to promote the resilience of ecosystems’.
more general sense to communicate a goal or in relation to human capital (such as
conservation partnerships and local communities) involved in the flow of ecosystem
services. A BESS workshop with researchers Volker Grimm and Hanna Weise highlighted
the multiple definitions used, but that resilience essentially encompasses three related
elements [5]:
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Resistance – the ability of a system to remain essentially unaltered after disturbance.
Recovery – the ability of a system to return to the previous state after disturbance.
Persistence – the ability of a system to maintain a state over time, which depends on
both resistance and recovery.
Others consider resistance to be a separate quality to resilience [4]. Theory on ecological
resilience suggests that gradual environmental changes and pressures might be having little
apparent impact on an ecosystem, until a sudden disturbance such as disease tips the
ecosystem into a different set of reinforcing processes. This can lead to a ‘regime shift’ with
a change in the assemblage of species providing ecosystem functions. This ‘alternative
stable state’ might be less favourable in contributing to the ecosystem services needed for
societal wellbeing. Management interventions to return the ecosystem to its previous state
might then be more costly than prevention or impossible [6].
Declining resilience of ecosystem functions.
Relatively low levels of biodiversity may be sufficient to provide
a range of ecosystem services under current environmental
conditions [2]. However, the rate and intensity of environmental
change is increasing, with future conditions likely to be very
different [2]. If species important for underpinning particular
services are lost or decline because of environmental change,
this could result in sudden declines in ecosystem services [2].
Dark Green Fritillary, Tom Oliver. However, if there are multiple species which perform a similar
function, but with different responses to environmental changes,
then the dominant species performing a particular function could switch. This is often
described as the ‘insurance effect’ provided by biodiversity. Ellen Fry and colleagues found
that having plant species with varying traits increases the resistance of chalk grassland to
drought and aids recovery. These functional traits of plants are characteristics that influence
their surroundings and impact on the ability of the system to deliver ecosystem services.
Tom Oliver and colleagues looked at trends over four decades in the abundance of animal
species that provide ecosystem functions in Great Britain [2]. They found that the resilience
of some ecosystem functions are being eroded faster than others [2]. Declines in groups of
species that are important for carbon sequestration and decomposition are small and have
been offset by arrivals of new species [2]. However, there have been significant net declines
in species that provide cultural values, pest control and pollination, suggesting an erosion of
the resilience of these ecosystem functions [2].
Dieback in the New Forest with evidence for threshold responses.
Forest dieback is occurring globally and is ongoing in the New Forest. BESS researchers
found that some areas of the New Forest dominated by beech in 1964 had become relatively
open grassland by 2014 [7]. The high death rates of large beech and oak trees were
associated with changes in other tree species, changes in the plant species at ground level
and an increase in grass cover. Importantly, these changes associated with tree death
occurred relatively abruptly. Only in areas where more than around 40% of the basal area of
trees were lost did the composition of other species change and grass cover increase.
These threshold responses occur when there is positive feedback, but they can be difficult to
detect without long term monitoring. This transition in the New Forest does not meet the
definition of an alternative stable state required by theory, because some of the disturbance
involved is ongoing grazing pressure rather than shorter-term ‘pulse’ disturbance [7]. Likely
causes of beech dieback include droughts combined with attack from pathogenic fungi.
Regeneration from seedlings is then prevented by pony and deer grazing. Beech makes up
a large proportion of canopy cover in the native woodlands of southern UK and has a low
tolerance for drought, so these UK forests may have low resilience to climate change.
2. Mechanisms underpinning the resistance and/or recovery of ecosystem functions to
[3]
environmental disturbances :
Species level mechanisms
 Sensitivity to environmental change
 Intrinsic rate of population increase
 Adaptive phenotypic plasticity – the ability to change to a changing environment
 Genetic variability
 Allee effects - make populations less likely to recover from small numbers
Ecological community level mechanisms
 A positive correlation between species’ importance for an ecosystem function and their
response to a given environmental change will lower resistance
 Network interaction structure
 Ecological processes supporting recovery, such as dispersal & establishment
 Functional redundancy - the insurance effect of biodiversity
Landscape level mechanisms
 Local environmental heterogeneity
 Landscape level functional connectivity
 Potential for alternative stable states
 Area of natural landscape cover
Maintaining resilience.
Management options and issues to consider include:
Awareness of the multiple definitions and uses of the term resilience. For example,
‘flood resilience’ encompasses many aspects of a local community, while ecological
resilience considers the ecosystems providing flood regulation services. CBESS and BESS
small grant research highlights how saltmarsh and mudflats have a direct role in natural
flood management and an indirect role through the regulation of greenhouse gases.
Understanding trade-offs between different services and for different groups of people [3].
Scenario setting, such as the DURESS scenarios for upland Wales [8], can highlight the
range of drivers involved and societal choices. There might be trade-offs between managing
for short term ecosystem functions and for long term resilience [3].
Making choices about the level and type of intervention desired by people and
appropriate for the landscape and resources available. For example, one response to beech
forest dieback could be to protect seedlings from grazing [7]. An alternative option would be
to view the New Forest as adapting to changing conditions, although this would involve
accepting reductions or changes in some ecosystem services [7].
Actions intended to increase resilience can meet other needs and goals as part of the
Ecosystem Approach [4]. Evidence is emerging from BESS research that increasing
connectivity in forest landscapes and freshwater shallow lake systems increases resilience.
Interventions that modify functional connectivity for one species can affect different species
and processes in different ways [9]. Planting wide buffers of deciduous woodland alongside
upland streams can potentially increase resilience and provide other benefits [10].
Identifying aims and awareness of the potential for unintended consequences for
biodiversity [1]. The particular concept of resilience will influence the management strategy
[4]
. Management interventions designed to strengthen resilience need to be carefully
selected so that they do not result in negative impacts on biodiversity [1].
Identifying the minimum thresholds for ecosystem functions and services that are
acceptable to society [3]. This involves interdisciplinary working and involvement of a wide
range of stakeholders, such as research by Wessex BESS on grassland restoration.
Actions targeting human and manufactured capital, such as urban design, influence
biodiversity and ecosystem functions [11]. For example, restoring park trails maintains
biodiversity, erosion control and cultural ecosystem services under climate change [12].
Justifying actions to promote resilience can be challenging when they can appear
redundant under current environmental conditions and within the short timescales typically
considered during decision making [3].
Monitoring to keep ecosystems within safe operating spaces is currently severely limited
and reporting about ecosystem services focuses on the short term [3, 4]. There is a need to
develop robust cost-effective indicators linked to the mechanisms underpining resilience [3].
References
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12.
Newton, A.C., Biodiversity risks of adopting resilience as a policy goal. Conservation Letters, 2016: p.
doi: 10.1111/conl.12227.
Oliver, T.H., et al., Declining resilience of ecosystem functions under biodiversity loss. Nature
Communications, 2015. 6:10122.
Oliver, T.H., et al., Biodiversity and resilience of ecosystem functions. Trends in Ecology & Evolution,
2015. 30(11): p. 673-684.
Newton, A.C. and E. Cantarello, Restoration of forest resilience: An achievable goal? New Forests,
2015. 46(5): p. 645-668.
Martin, P. Just what is resilience, anyway? Ecology for a crowded planet blog post.
https://ecologyforacrowdedplanet.wordpress.com/2015/06/25/just-what-is-resilience-anyway/.
Walker, B. and D. Salt, Resilience thinking: sustaining ecosystems and people in a changing world.
2006: Island Press.
Martin, P.A., et al., Stand dieback and collapse in a temperate forest and its impact on forest structure
and biodiversity. Forest Ecology and Management, 2015. 358: p. 130-138.
Prosser, H., T. Pagella, and I. Durance, Upland scenarios: what will the future look like? DURESS
project report card. 2015.
Harrison, L.J., P. White, and S. Odell, Connectivity and ecological networks. Landscape Institute
Technical Information Note. 01/2016 2016.
Thomas, S.M., S.W. Griffiths, and S.J. Ormerod, Beyond cool: adapting upland streams for climate
change using riparian woodlands. Global Change Biology, 2015. 22(1): p. 310-324.
Cox, D.T.C., et al., Movement of feeder-using songbirds: the influence of urban features. Scientific
Reports, 2016. 6: p. 37669.
Tomczyk, A.M., P.C.L. White, and M.W. Ewertowski, Effects of extreme natural events on the provision
of ecosystem services in a mountain environment: The importance of trail design in delivering system
resilience and ecosystem service co-benefits. Journal of Environmental Management, 2016. 166: p.
156–167.
Prepared by Laura Harrison, Anna Middlemiss and Charlie Parkin, with thanks to Ambroise Baker,
Hannah Burton and Philip Martin.