APPENDIX 3 - Genetics, fragmentation and climate change - implications for restoration and rehabilitation of local indigenous vegetation communities
Two primary threats and their interactions
need to be recognised by revegetation practioners. These are fragmentation
and climate change.
Effect of fragmentation on genetic diversity.
The concept of confining seed collection to a ‘local provenance’
area (to ensure local adaptation is maintained) has been widely adopted
by plant-based restoration practitioners. However, the paradigm of collecting
very close to the restoration site is no longer considered useful. Firstly,
scientists agree that plant local adaptation is not as common as many
believe. Secondly, many practitioners now understand that a ‘local’
genotype may occur over wider areas (i.e. from 10s to 100s of km) depending
on the species and its biology. However, in a largely cleared landscape,
small fragments are at risk of elevated inbreeding when populations of
a species drop below threshold numbers, which can be different for every
species. As inbred seed may fail to reinstate functional and adaptable
plant populations, in general it is best to collect seed from larger,
higher density stands. This means that in fragmented landscapes where
vegetation stands are smaller, less dense and more isolated, collecting
seed from wider distances and multiple sources will be necessary to capture
sufficient genetic diversity to rebuild functional communities. This seed should be multiplied in regional seed production areas, however, to avoid
overharvesting from remnants.
Examples of seed production
Examination of Australian ecosystems shows that many indigenous species
have endured ancestral extremes of climate well beyond predicted climate
change scenarios. However, accelerated climate change is a serious emerging
problem. Some species will be impaired by increasing ocean temperatures,
acidity and marine, freshwater and terrestrial habitats will be lost in
some locations due to sea level rise. Many river channels, lakes and wetlands
may also be affected by drying or its consequences such as increase salinity
- and cold-adapted species will be lost at colder, higher elevations where
there is nowhere higher for them to migrate as climate warms. Indeed,
even conservative global warming scenarios suggest that a wide range of
local environments to which species may have adapted will change dramatically.
Although we cannot precisely predict the type and scale of risks that
ecosystems face because only a small proportion of species has been individually
studied, we know that some species may be lost from their current locations
while others will colonise new areas, altering local species assemblages.
We also know that the effect of climate change will be particularly strong
when combined with high levels of fragmentation.
Some species may have sufficient inherent ‘adaptive plasticity’
to persist as climates change, as has been demonstrated from translocation
experiments and detailed pollen analysis of past environments. That is,
an individual plant may be able to adjust its form by mechanisms such
as reducing its leaf size, increasing leaf thickness or altering flowering
and emergence times. But in many cases, persistence may depend on a species’
capacity for genetic selection or adaptation, which in turn depends on
population size and the diversity of the genes available.
Species that have large, connected populations, a wide climatic range,
naturally high dispersal characteristics and whose populations have many
genes in common are likely to have a higher chance of genetically adapting
to the new environments or migrating as their climate envelope moves.
Conversely, species with low pollen and seed dispersal characteristics,
that occur naturally in ‘islands’ or ‘outliers’
or that have been isolated through land clearing or river regulation,
for example, may be less able to adapt or migrate in response to climate
Implications for restoration and rehabilitation.
Techniques and protocols are emerging to guide the collection of genetically
diverse material to use in revegetation to enhance a species’ adaptive
potential. In extensive, intact indigenous habitats where species and
populations are likely to have a greater capacity to adapt unaided because
of high connectivity, interventions to enhance adaptive potential are
unlikely to be needed. But where landscapes or waterscapes remain largely
fragmented, interventions to assist genetic adaptation are expected to
be beneficial. This means that, while the local gene pool still has potential
to play a major role in adaptation, it is prudent to consider including
at least a small amount of germplasm of the same species from a ‘future
climate’ – that is, a region with a climate similar to that
which is predicted for the area being restored. Research is underway to
test some of these new approaches and it is hoped that ‘rules of
thumb’, will eventually be developed. Meanwhile, researchers are
designing protocols and proformas for appropriately documented and registered
‘citizen science’ trials integrated into low risk restoration
settings. Participation in such trials will enable groups to actively
test a range of recommendations on their sites while also optimising opportunities
for improved science and practice.
Tools for assessing climate-readiness in
relation to genetics
Some tools are available to help restoration planners undertake what could
be called ‘climate readiness’ analysis at the planning stage.
Firstly, restoration practitioners are encouraged to seek out predictions
of locations where ecosystems are likely to be affected by climate change.
Secondly, practitioners are encouraged to liaise with researchers to gain
a better understanding of predicted responses of species to both fragmentation
and climate change and to identify the relative risks of a range of options
relating to the deliberately movement of genetic material in restoration
projects. (Genetic analysis can be undertaken by a range of research institutions
and is increasingly affordable for practitioners. This cost reduction
is increasing numbers of species being studied while rapid improvements
in the effectiveness and efficiency of genetic testing tools is also occurring.)
Web-based tools are also readily accessible for identifying whether the
species currently occurring in the vicinity of your site will still be
suited to climates predicted to occur at your site in the future. One
of the most important of these is the Atlas of Living Australia website
can help practitioners identify the natural geographic range of a species
and whether it may have potential to tolerate the conditions predicted
to occur under climate change scenarios which themselves are mapped on
the website http://www.climatechangeinaustralia.gov.au/en/.
An explanation of how these tools can be combined is found in Booth
et al. (2012).
Proposed propagule sourcing strategies to build climate-readiness into
restoration through ensuring genetic diversity include: composite provenancing
(Broadhurst et al. 2008), admixture provenancing
(Breed et al. 2013), predictive provenancing (e.g.
Crowe & Parker 2008), and climate adjusted provenancing
(Prober et al. 2015, Fig 4). Application of any
such models should be undertaken within a risk management framework that
considers the potential negative effects of inbreeding and outbreeding
depression, interpreted in a manner clearly understood by practitioners.
It should also include long-term monitoring (i.e. at least a decade) to
enable lessons learned to be captured for both restoration and climate
Practitioners designing planting lists need to bear in mind, however,
that it is impossible to be certain of the changes that will occur. Different
species will respond to climate change in different ways and at the moment
there is no easy way to predict this. Furthermore, temperature and rainfall
are not the only important predictors. A range of physical (e.g. soils)
and biological factors (e.g. dispersal) – which themselves may or
may not be affected by a changing climate - can also have important roles
in influencing the distribution of a species. While some caution will
always be required, a balanced approach in fragmented areas would see
the restoration plan specify the use of locally occurring species (preferring
germplasm from larger populations, even if somewhat more distant) and
where advised, formally trialling the inclusion of some germplasm from
future climate locations. Such a combined approach – coupled with
optimising connectivity to the extent possible – is likely to improved
opportunities for natural adaptation should it be required.
4. Provenancing strategies for revegetation
(Reproduced here from Prober et al 2015.] The star indicates the site
to be revegetated, and the circles represent native populations used as
germplasm sources. The size of the circles indicates the relative quantities
of germplasm included from each population for use at the revegetation
site. In the case of the climate-adjusted provenancing the relative quantities
of the germplasm from the various populations will depend upon factors
such as genetic risks, and the rate and reliability of climate change
projections. For simplicity this represents the major direction of climate
change in a single dimension (e.g. aridity, to combine influences of increasing
temperature and decreasing rainfall), but multiple dimensions could be
considered as required.
Booth, T.H., Williams, K.J. and Belbin, L. (2012)
Developing biodiverse plantings suitable for changing climatic conditions
2: Using the Atlas of Living Australia. Ecological Management & Restoration
Breed, M.F. Steed, M.G., Otewell, K.M., Gardner,
M.G., and Lowe A.J. (2013) Which provenance and where? Seed sourcing strategies
for revegetation in a changing environment. Conservation Genetics
Broadhurst, L.M., Lowe, A.J., Coates, D.J., Cunningham,
S.A, McDonald, M., Vesk, P.A., and Yates, C.J., (2008) Seed supply for
broadscale restoration: maximizing evolutionary potential. Evol. Appl.
Crowe, K.A., and Parker, W.H. (2008) Using portfolio
theory to guide reforestation and restoration under climate change scenarios.
Climatic Change 89: 355-370.
Prober SM, Byrne M, McLean EH, Steane DA, Potts BM,
Vaillancourt RE, Stock WD (2015) Climate-adjusted provenancing: a strategy
for climate-resilient ecological restoration. Frontiers in Ecology
and Evolution 3: Article 65. http://journal.frontiersin.org/article/10.3389/fevo.2015.00065/full#