an overview of biodiversity conservation in mauritius
TRANSCRIPT
An overview of biodiversity conservation in Mauritius
F. B. Vincent FLORENS
Department of Biosciences
University of Mauritius
OutlineIntroducing Mauritius: Basic facts about terrestrial biodiversity
Conservation challenges in Mauritius laboratory of extinction ?
Conservation successes in Mauritius laboratory of conservation ?
Selected case studies of plant conservation and ecological restoration
Remaining challenges, lessons and conclusions
Discovered by the Portuguese in early 16th CenturyColonised: 1638 Dutch - 1722 French - 1810 British
~ 7.6 MY old Volcanic island ~900 km East of MadagascarMaximum altitude 828m1865 Km2
Mauritius
Mauritius Biodiversity overview
Florens 2013. In Sodhi et al. (eds) Conservation Biology: Voices from the tropics.
Biodiversity EcosystemsA wealth of different ecosystems from dry coastal vegetation to wet tropical and mossy forests, marshes etc
0
1
1600 1620 1640 1660 1680 1700 1720 1740 1760 1780 1800 1820 1840 1860 1880 1900 1920 1940 1960 1980
Approximate year of extinction
Raven Parrot 1674
Ren hen1693
Tortoises1840
Dodo1700
Grey Parrot1759
Pigeon Hollandais1826
Roussette1864
P Schouten
Other paintings JHume
Gibbus1914Tropidophora
carinata 1881
Burrowing boa 1974
Extinctions rates
0
10
20
30
40
50
60
70
80
90
100
Plantes Reptiles Oiseaux Escargots
Pour
cent
age
d'ex
tinct
ion
Plants Reptiles Birds Snails
Perc
enta
geof
ext
inct
ion
From bad to worst....Habitat destruction (Major cause of extinctions)
Habitat fragmentationMinimum viable populations?
(
Ahead of the world in terms of habitat destruction and fragmentation
Predictions rather grimEcosystem degradation has been and is predicted to continue to be most rapid in developing or relatively low income countries (Laurance 2001 TREE)
Overexploitation: Edible palms
As early as 1638 some native species started to become rare in some areas, like the palmiste blanc in Port Louis
in 1670
Alien species*Plants (23 seriousinvader species)
Lantana camara
Psidium cattleianum
Feral pig Macaque .
Animals
* Worst threat on most oceanic islands(Caujape-Castells et al 2010 PPEES)
Extreme invasion by alien plantsUnderstorey heavily dominated by alien plants
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
11000
1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 >20
Diameter size class (cm)
Num
ber o
f ind
ivid
uals
NativeAlien
Natives Aliens
)
Alien plant invasion progress over 20 years
> 2.5 cm dbh
Sites Lorence & Sussman
This study
% alien plants
Brise Fer 20.8 27.5
Bel Ombre 34.8 60.7
Native species richness
Brise Fer 49 42 7.4 n.s.
Bel Ombre 56 55 7.7 n.s.
Native density (1000 m2)
Brise Fer 76.2 58 9.1Bel Ombre 71.5 63 11.2
Acute conservation
Pandanus pseudomontanus
Dombeya mauritiana1 survivor in the wild
Hyophorbe amaricaulisRarest species worldwide
Many species on the brink, including CWR
Rarest screwpine in the world
Conservation Management Areas
Fenced to exclude alien pigs (Sus scrofa) and Java deer (Rusa timorensis)
All invasive alien plants weeded
Reproductive output (S. grandiflorum
Flowering is more abundant in areas without alien plants*(U122,78 = 3520.5; P = 0.002)
Fruting is in average 37 times higher in managed areas* (U140,135 = 6662.5; P< 0.001)
* Baider & Florens (2006) In Laurance & Peres Emerging threats to tropical forests. Chicago Univ Press
Invasion strongly reduces reproductive output
Growth and mortality of Sideroxylon grandiflorum
Site NMean growth rate/year
(cm ± 95%CI)
Non-weeded 125 0.046 ± 0.046
Weeded 155 0.112 ± 0.042
Higher growth rate in managed (weeded) sites
Site N Mean mortality/year
Non-weeded 140 13 2.7%
Weeded 160 1 0.16%
Higher mortality rate on invaded forests
Mean growth rate of all woody native species
Non weeded Weeded
NumberAverage(dbh, mm) -95% 95% Number
Average(dbh, mm) -95% 95%
Brise Fer 795 0.10 0.08 0.12 686 0.58 0.45 0.72
Mare Longue 1353 0.08 0.06 0.11 995 0.44 0.35 0.53
Community changes over 4 years
050
100
150200250300350
400450500
0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10 to15
15 to20
> 200
50
100150200
250300350400
450500
0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10 to15
15 to20
> 20
0
50
100
150
200
250
300
350
400
450
500
0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10 to15
15 to20
> 20
Weeded Not weededB
rise
Fer
Mar
e Lo
ngue
050
100150
200250
300350
400450
500
0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10 to15
15 to20
> 20
Num
ber o
f ind
ivid
uals
DBH class (cm)
20032007
3 0
318
00
50
100
150
200
250
300
350
Managed Invaded
Indi
vidu
als/
ha
AdultJuvenile
Invasion effect on native Cyathea spp. (tree ferns)
Comparison between 1 ha invaded and 1 ha weeded(Thormann, Baider & Florens unpubl data)
3 0
318
00
50
100
150
200
250
300
350
Managed Invaded
Indi
vidu
als/
ha
AdultJuvenile
Invasion effect on native Cyathea spp. (tree ferns)
Comparison between 1 ha invaded and 1 ha weeded(Thormann, Baider & Florens unpubl data)
(Bindewald, Baider & Florens unpubl)
Large epiphytic ferns
Population recovery within 24 years
0
20
40
60
80
100
120
140
160
180
Non-weeded Weeded 1996 Weeded 1986
Den
sity
of a
dult
Asp
leni
um n
idus
per
ha
aa
b
Kruskal-Wallis test:H = 154.49; p < 0.001 {0.1ha plots}
0
50
100
150
200
250
Non-weeded Weeded 1996 Weeded 1986
Den
sity
of a
dult
Mic
roso
rum
pun
ctat
um p
er h
a
a
a
bKruskal-Wallis test:H = 122.73; p < 0.001 {0.1ha plots}
Asplenium nidus
Microsorum
Butterflies: Species richness
Florens et al 2010. Biodiversity and Conservation
-0.5
0.5
1.5
2.5
3.5
4.5
5.5
6.5
7.5
8.5
9.5
10.5
11.5
12.5
1 5 9 13 17 21 25 29 33 37 41
Estim
ated
spe
cies
rich
ness
(Mao
-Tau
)
Cumulative number of transects
Alien-invaded forestNon-invaded forest
Butterfly: Abundance
Sites Weeded forest
Non-weededforest
Bel Ombre (Bellouguet) 6.75 0
Bel Ombre (Fixon) 4.5 0.17
6 0.17
2.83 0.33
Brise Fer 1 (Low canopy) 6 0.40
Brise Fer 2 (High canopy ) 7.67 0.50
Macchabé 8.75 0.50
Mare Longue 5 0.40
Total 5.94 0.31
Average density of butterfly per transect
Florens et al 2010. Biodiversity and Conservation
Namah, Baider & Florens unpubl
Abundance of birdsMethod: Fixed radius point counts, with a radius of 20 m (Hostetler & Main, 2008)
Exclusion fencing as conservation measure
Fenced to exclude alien pigs (Sus scrofa) and Java deer (Rusa timorensis)
Mare Longue
0
50
100
150
200
250
10/11
/03
10/12
/03
10/1/
04
10/2/
04
10/3/
04
10/4/
04
10/5/
04
10/6/
04
10/7/
04
10/8/
04
10/9/
04
10/10
/04
10/11
/04
10/12
/04
10/1/
05
10/2/
05
10/3/
05
Num
ber o
f 'liv
e' a
rtific
ial s
eedl
ing
Not weeded + Not fenced
Weeded + Fenced
Exclosures are ineffective incontrolling trampling /uprooting damage by largealien mammals
Brise Fer
0
50
100
150
200
250
18/12
/03
18/1/
04
18/2/
04
18/3/
04
18/4/
04
18/5/
04
18/6/
04
18/7/
04
18/8/
04
18/9/
04
18/10
/04
18/11
/04
18/12
/04
18/1/
05
18/2/
05
Num
ber o
f 'liv
e' a
rtific
ial s
eedl
ing
Not weeded + Fenced
Not weeded + Not fenced
Alien guava fruiting season
Seed
ling
num
ber
Influence of pig and deer exclosures
Date
Exclosure + alien plants weeding
No exclosure, no weeding
Exclosure only
No exclosure, no weeding.
Alien guava fruiting season
Rattus rattus and R. norvegicus
Seed predation
Canarium - Burseraceae Mimusops - Sapotaceae
Alien rats
0
150
300
450
600
750
900
1050
1200
1350
1500
Seedlings and non-reprodutive trees
Reproductive trees Dead adult trees
Freq
uenc
y of
Pan
danu
s va
nder
mee
schi
i 1982
1993
2004
Screwpine (Pandanus vandermeeschii)
Hare and rat eradication
Predator control: e.g. Hare and rat
Re-introduction/augmentation programsMauritius is well known for some conservation successes
4 birds
Captive breeding
Re-introduction
Artificial nests (nest boxes)
Supplementary feeding
Predator control
< 30 birds 18 birds
Now 600Now 440 Now 450
Most of the restoration activities and research are however carried out on offshore islets
Native habitats on mainland Mauritius harbor more endemic and threatened species (1-2 orders of magnitude more compared to the islets), deserving far greater conservation attention
Restoration sites
Initial alien weed control (Mainly Psidium cattleianum)
Herbicide use:
Cheaper
Less collateral damage
Quickly adopted by private sector
Num
ber o
f Ha
rung
ana
sapl
ings
per
plo
t
0
5
10
15
20
25
30
Before After
U14,14 = 7.5; p < 0.0001
Min-Max25%-75%Median value
Mea
n gr
owth
rate
in tr
unk
girth
(mm
/yr)
02468
101214
Haru
ngan
aSi
dero
xylo
nLa
bour
d onn
aisia
Hanc
eaAn
tides
ma
Aphl
oia
Orfil
eaLu
dia
Nuxi
aSe
curin
ega
Vepr
isGa
e rtn
era
Anti r
hea
Mol
inae
aM
imus
ops
War
neck
eaCn
estis
Leea
Coffe
aDi
ospy
ros
Todd
alia
Conclusions
1. Control of invasive alien plants
2. Control and eradication of invasive alien animals
3. Population reintroduction/augmentation or analogue introduction
Grim situation attracted considerable conservation efforts (summarized in Jones 2008)
As a result, Mauritius now contributes to the advancement of restoration and conservation science through serving as a laboratory to test various approaches
ConclusionsMany species, including threatened ones, can recover dramatically as a consequence of the sole removal of invasive alien plants.
It does not suffice to set protected areas. Conservation management within these areas is important. Invasions are worsening worldwide, and Mauritius provides a window into the future of other countries.
Our findings also indicate that imminent plant extinctions can be averted by little more than timely control of the invading plants.
Use of evidence-based approach to restoration and conservation is much easier said than done