1. “Searching for universal early-warning
indicators of desertification: anticipating
tipping points at ecosystem level ”
Cristina Branquinho1, Pedro Pinho1,2, Alice Nunes1,3,
Paula Matos1,3, Melanie Batista1, Adriana Silva1,
Andreia Ferreira1 and Lúcio do Rosário4
1Universidade de Lisboa;
2Universidade Técnica de Lisboa;
3Universidade de Aveiro; Ciência 2007
4Instituto de Conservação da Natureza e Florestas; LTER/BIA-BEC/0048/2009
PTDC/AAC-CLI/104913/2008

2. Drylands
• Cover about 41% of Earth’s land surface supporting over 38% of the global
human population
• Semi-arid areas are the most vulnerable to DLD
Millennium Ecosystem Assessment (2005) Ecosystems and Human Well-Being: Desertification Synthesis (World Resources
Institute, Washington, DC).

3. Which type of Indicators should we use?

4. Mechanisms of transitions between ecosystems states and tipping points
An ecosystem experiences a shift to a new state, with significant changes to
biodiversity and the services to people it underpins, at a regional or global scale.
Tipping points also have at
least 1 of the following
characteristics:
✤ The change becomes self
perpetuating (deforestation
reduces regional rainfall,
which increases fire-risk,
which causes forest dieback
and further drying).
✤ There is a threshold beyond
which an abrupt shift of
ecological states occurs.
✤ The changes are long-
early warning lasting and hard to reverse.
✤ There is a significant time
lag between the pressures
and the appearance of
impacts.
Secretariat of the Convention on Biological Diversity (2010) Global Biodiversity Outlook 3.

5. Ecosystem functioning is extremely complex and thus monitoring the effects of
environmental change factors in ecosystems in an integrative perspective can
make use of ecological indicators.

6. Hypothesis/Assumptions
• It is possible to find early warning indicators of
tipping points.
• Those indicators are most probably ecological
indicators which reflect in overall an integrated
response of the ecosystem.
• Indicators based on biodiversity changes can be
one of those indicators.
• Without time we can use gradients in space to
give us a clue about possible good indicators.

7. Does all species have the same value?
Ecosystem Processes
Biodiversity
M. Scherer-Lorenzen, (2005), BIODIVERSITY AND ECOSYSTEM FUNCTIONING: BASIC PRINCIPLES, in Biodiversity: Structure and Function, [Eds. Wilhelm
Barthlott, K. Eduard Linsenmair, and Stefan Porembski], in Encyclopedia of Life Support Systems (EOLSS),, Oxford ,UK

8. Functional Diversity – Potentially Universal
Functional diversity: groups according to common response to the
environment and/or common effects on ecosystem processes/functions
• Has been shown to relate
with several environmental
constraints (e.g. nutrient
availability, grazing, fire,
etc.)
•
• Independent from local
communities composition -
potential to be universal
Díaz, S. & Cabido, M. (2001) Trends in Ecology & Evolution 16, 646-655.
Lavorel, S. et al. (2007) Plant Functional Types: Are We Getting Any Closer to the Holy Grail? Springer-Verlag, Berlin Heidelberg. pp.
149-160.

9. Study site
Portugal susceptibility to DLD
Aridity Index
sub-humid and humid
dry sub-humid
semi-arid
 Mediterranean climate with Montado, an agro-pastoral system dominated by
holm-oak (Quercus ilex L.) woodlands
 Study transition in a spatial aridity gradient
Source: Autoridade Florestal Nacional

10. Selection of the DLD gradient
Homogeneous conditions
Stratified sampling (precipitation,
(Holm-oak open woodlands, grazing
temperature, aridity indices, etc.)
intensity, lithology, slope, fire
occurence, etc.)
precipitation soil organic C
Aridity Evapotransp.
Susceptibility Temperature
a
Random selection of sites (≥60)

11. establishing relation between climate and biological variables
1) Lanscape scale – remote
sensing analysis
2) Using plant Functional
diversity
3) Using lichen Functional
diversity
desertification and land-degradation gradient

12. vegetation structure
1) Landscape - Canopy Cover
Dry
Frequency
Intermediate
Wet
Canopy Area

13. 1) Landscape - NDVI 556 mm

14. 2) Using Plant functional diversity
Legum. Non legum.
• Point-line intercept transect method
• A priori functional groups (e.g. life cycle, life form, etc.) and measured traits (e.g.
SLW, height, etc.)

15. 2) Plant functional pattern along a precipitation gradient
Perennial 31 sites
graminoids Comp_un analyzed
0.6
27
and N-fixing Leg_un
0.4
Comp_pe
5
Gram_pe 22 Leg_an 18
0.2
11
NMDS2
7 24
28
26
31
25
8
shrubs
4
0.0
17 Othe_un
13
6 Othe_an
Comp_an
12
16 30 Othe_pe
Gram_an 15 Gram_un
Comp_ab 14
Othe_ab 29 20
-0.2
2 3
Gram_ab 9 10
19 23
Annual 1
21
-0.4
graminoids Leg_pe
and biennials
-0.6
-0.5 0.0 0.5 1.0
NMDS1

16. 2) Using Plant functional diversity 24 sites analyzed
Plant functional shifts
80
Functional groups cover
60 Annual
graminoids +
Plantago sp.
(%)
40
Perennial
graminoids +
20
Annual N-
fixing
0
500 550 600 650
Last 50 Years average precipitation (mm)

17. 2) Using Plant functional traits 14 sites analyzed
40
SLA T. barbata (m2kg-1)
30
20
10
0 Measured only for 2 species
500 525 550 575 600 625 650
Last 50 yr precipitation (mm)
25
Veg. height V. myurus (Q90)
20
15
10
5
0
0.4 0.5 0.6 0.7 0.8
Aridity index
Measured for all species

18. 3) Using lichen Functional diversity
Standard
“European
method”
L DV (lichen
diversity value)
Asta, J., et al, 2002. Monitoring with Lichens, Kluwer Academic Publisher.

19. 3) Using lichen Functional diversity
lichens functional diversity as early warning of
desertification
Hygrophytes
Xerophytes
annual average
precipitation (mm)

20. 3) Using lichen Functional diversity
Does lichen diversity respond to climate over time?
Before: 2002 After: 2003

21. nal Remarks
Functional diversity (plants and Lichens) seems to be a
good candidate for early warning since it respond to
changes in climate and desertification gradients.
Moreover has the potential to be universal.
We are contributing to the 3 UN "sister Conventions":
on biodiversity-CBD, climate change-UNFCCC and
desertification-CDD, that relay in ecological indicators of
biodiversity and ecosystem goods and services
evaluation.
We are willing to test this hypothesis in other countries.
Thank You!