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1. Definition
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Name
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ECOSYSTEM
RESILIENCE
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Brief
definition
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Ecosystem
resilience describes the intrinsic regeneration potential
of a vegetation community or an ecosystem after endogenous
disturbance, i.e. the degree, manner and pace of restoration
of the structure and function of the original ecosystem
after disturbance.
Concepts
of ecosystem resilience may consider manifold processes
at a large field of spatial and temporal scales, ranging
from microbiological activity of soil at patch level
to changes of vegetation structure and functioning
at regional scale.
In
this case the indicator description refers to changes
in vegetation cover and functioning from catchment
to Mediterranean wide scale, expressed in changes
of rain use efficiency.
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Unit
of measure
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Rain
use efficiency (RUE) is a synthetic index (lumped
parameter) relating an important function of land
(NPP) to the principal controlling factor in drylands
(rainfall).
The
overall effect is reflected in a local decline of
the ratio of actual evapo-transpiration to precipitation:
RUE**AET = AET / P
In
several studies it was shown that spatially distributed
estimates of RUE can be derived from spatial anomalies
of vegetation density, that can be operationally derived
from remote sensing data at different spatial and
temporal scales over decades. Thus RUE can be re-written
as RUE proxy1 = sum NDVI / P
Similarly
cumulated or mean annual values of Green Vegetation
fraction have been used, with the assumption that
these values were less influenced by soil colour:
RUE proxy2 = sum GVF / P
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Spatial
scale
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Catchment
scale to Mediterranean wide
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Temporal
scale
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Yearly
assessment of RUE over decades (tens of years)
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2.
Position within the logical framework DPSIR
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Type
of Indicator
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State/Impact
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3.
Target and political pertinence
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Objective
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Land
degradation state and impact assessment
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Importance
with respect to desertification
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Long
term trends of decrease in vegetation cover and changes
in its functioning are among the most important indicators
proposed for regional scale long term early warning
and response systems (LTEWRS).
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International
Conventions and agreements
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The
UNCCD emphasizes that combating desertification must
be tackled within the general framework of actions
to promote sustainable development.
Furthermore
the UNCCD requires the creation of a working method
to lay the foundation and provide the cognitive elements
required to implement the convention at a regional
level (ICCD/COP(4)/3/Add.3 (B).
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Secondary
objectives of the indicator
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4.
Methodological description and basic definitions
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Definitions
and basic concepts
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The
underlying concept relates land degradation to a complex
of processes that leads to a shift in temporal and
spatial patterns of water resources availability at
time scales of years to decades. These processes alter
the relative importance of the main water balance
components towards locally increasing water losses
by runoff and soil evaporation and decreasing transpiration
by plants.
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Benchmarks
Indication of the values/ranges of value
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Negative
slope of trend line over the longest possible time
series of yearly RUE, respectively RUE derived land
condition indices (M. Boer, 1999).
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Methods
of measurement
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Ratio
of remote sensing derived annual vegetation cover
and annual precipitation.
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Limits
of the indicator
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A
full interpretation of RUE variations would require
information on topography, soil texture, soil fertility,
vegetation type, human population and management practices
among others, which for large areas is not easily
accessible in suitable formats.
It
is evident that a single index or variable can hardly
represent the complex phenomena and interactions of
desertification. Nevertheless, reported results suggest
that it is possible to use reduced RUE values as an
indicator of areas subject to desertification; once
identified these regions could be targeted for more
detailed studies (high resolution satellite monitoring
and/or field studies).
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Linkages
with other indicators
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Vegetation
cover rs, Rainfall
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5.
Evaluation of data needs and availability
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Data
required to calculate the indicator
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Primarily
optical remote sensing data, preferably corrected
to ground surface reflectance, in order to derive
vegetation cover values. Gridded data of annual rainfall
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Data
sources
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Time
series of Landsat-TM data, NOAA-AVHRR, SPOT VEGETATION
and in the future of MODIS, MERIS.
Long
term archives of climate data from various national
and international archives are available
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Availability
of data from national and international sources
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Climate
data: e.g. JRC MARS, University of East Anglia, regional
and national meteorological services.
Remote
sensing data: Availability of calibrated data of fractional
vegetation cover is limited. Time series of reflectance
channels and vegetation indices are available from
agencies such as ESA (ENVISAT), USGS (NOAA AVHRR pathfinder,
TERRA-MODIS), EC JRC (SPOT VEGETATION). Archived Landsat-TM
data are sold at acceptable prices by commercial providers
or can be made available by national and regional
mapping or environmental agencies.
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6.
Institutions that have participated in developing the indicator
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Main
institutions responsible
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Institute
for Environment and Sustainability, DG JRC, European
Commission, Ispra, Italy
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Other
contributing organizations
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CNRS
Lyon, F; CSIC Almeria, E;
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7.
Additional information
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Bibliography
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Le Houérou H. N., 1984 - Rain-use efficiency
: a unifying concept in arid-land ecology. J. of Arid Lands,
7, 213-247
Boer M. M., 1999 - Assessment of dryland
degradation: linking theory and practice through site
water balance modelling. Ph D Thesis, Faculteit Ruimtelijke
Wetennschappen Universiteit Utrecht, ISBN 90-6809-273-1
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Other
references
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Contacts
Name and address
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EC,
DG Joint Research Centre
Institute for Environment and Sustainability
Stefan Sommer
stefan.sommer@jrc.it
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