Technical Aspects of Offsets an approach to comparing the amounts of biodiversity losses or gains

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Technical Aspects of Offsets - an approach to
comparing the amounts of biodiversity losses or
gains

• David Parkes
• Victoria, Australia
• Kerry ten Kate, Forest Trends
• BBOP Learning Network
• Pretoria, South Africa - September 2006

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No Net Loss?
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(No Transcript)
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Key technical considerations

• Location of potential impact and offset sites
• the extent of direct and indirect impacts (Jon)
• biodiversity values at the sites and the nexus
  between these (Jon)
• ecosystem function consequences at the impact
  site and requirements at the offset site (Wayne)
• socio-economic consequences
• regional context

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Key technical considerations

• Options for achieving an offset
• management of habitat and/or the risks to it
• feasibility of these options
• sustainability of these options (Bruce)

• Accounting for the amount of losses and gains
• developing a practical surrogate for
  biodiversity gains and losses
• comparing between sites and ecotypes
• identifying whether gains are additional to
  existing

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Basic premise for comparing amounts use
observable physical habitat components
may be - structurally-based (e.g. cover of
plant lifeforms) - species-based (e.g.
diversity of key groups lack of weeds) -
dynamics-based (e.g. recruitment maturity) -
functional-based (e.g. litter soil integrity
nitrogen fixers)
- to be determined with expert local knowledge of
ecosystems (does the suite of components
provide an adequate surrogate for species
expected to use the site?)
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Basic premise for comparing amounts use
observable physical habitat components in a
condition metric (standardised for each
habitat type using its benchmark)
- need to choose practical measures for each
component and combine in a weighted index
- a benchmark is the average for these components
for fully natural stands of the original
habitat type at the site - these averages may
be based on site data or inferred from historical
and ecological insights
- benchmarks are just reference points they are
not necessarily the management objective (or even
achievable)
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Basic premise for comparing amounts use
observable physical habitat components in a
condition metric (standardised for each
habitat type using its benchmark) that
enables comparison of the amount of change
in condition between management options
between sites
losses can be full or partial reduction in
condition scores gains can be - expected
increase in scores after appropriate change to
mgt, - expected benefit of averting the risk of a
future loss
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Basic premise for comparing amounts use
observable physical habitat components in a
condition metric (standardised for each
habitat type using its benchmark) that
enables comparison of the amount of change
in condition between management options
between sites
aim for practical, measurable, comparable
..whilst retaining connection to ecological
insight
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Vegetation / Habitat Condition- Victorian system

• one Habitat Hectare
• one hectare of native vegetation which
  retains the average characteristics of a mature
  and apparently long-undisturbed stand of the same
  vegetation type
• - used for offsets, incentive mechanisms
  (auctions), and regional indicators

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Habitat Score

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Undisturbed vegetation
Habitat score 0.90
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Reduced quality of vegetation in cleared
landscapes
Habitat score 0.50
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Reduced quality of vegetation in cleared
landscapes
Habitat score 0.25
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Considering change in condition for the purpose
of- assist in choosing conservation actions-
more objective basis for quantifying the balance
between losses gains
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Habitat condition how full is the glass?
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Habitat condition how full is the glass?
a dynamic situation
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Estimating the potential of a candidate offset
site
1. current score 2. prognosis What is the current
situation with regenerative and degenerative
processes? What is the risk of future additional
impacts? 3. intervention Can we change the net
outcome? 4. amount How much change can be
achieved?
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Scoring gains
A standard period can be used to estimate gains
from changed management of vegetation, for
example
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potential improvement gain
projected gain from active management
Habitat Gain
habitat
score

potential maintenance gain
projected loss from allowable uses Or
probability of loss from future events
0
10 yr
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Comparing habitat volumes translating this
into area ratios
1 - Habitat Condition 0 -
LOSS AREA X TOTAL HABITAT SCORE
Loss from clearing
? 10 yr
GAIN AREA X HABITAT SCORE INCREMENT
1 - Habitat Condition 0 -
Gain from improvement and averted risk
? 10 yr
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Mitigation ratio

• basic ratio established
• area of offset site is typically greater than
  area of impact site
• are additional multipliers needed to set the
  final mitigation ratio?
• risk of offset failure?
• punitive damages ?
• precautionary principle?

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Key technical considerations

• Location of potential impact and offset sites
• the extent of direct and indirect impacts (Jon)
• biodiversity values at the sites and the nexus
  between these (Jon)
• ecosystem function consequences at the impact
  site and requirements at the offset site (Wayne)
• socio-economic consequences
• regional context