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 (Masacrenes islands)

Myers et al., 2000, Nature 403: 853-585

Mauritius Biodiversity overview

Florens 2013. In Sodhi et al. (eds) Conservation Biology: Voices from the tropics.

691 species (39.5 % endemism)

Biodiversity Angiosperms

Biodiversity - Birds42 species (33% endemism)

Biodiversity- Reptiles20 species (80% endemism)

Biodiversity EcosystemsA wealth of different ecosystems from dry coastal vegetation to wet tropical and mossy forests, marshes etc

Dodo: Symbol of human-caused extinction

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)

Rate of invasion by alien plants of native forests

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

Effect of weeding on woody plants

Results: Individual and population level(Sideroxylon grandiflorum Tambalacoque)

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

Predator control

Traps (rat, mongooseTrap (Macaque)

Poison

stations (rat)

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

2008

Land tortoise analogue species

2002

2010

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

Regular maintenance weeding to control re-infestation

Harungana madagascariensis (Hypericicaceae)

(1995)

(+ 15 years)

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

Recent policies

Government policy:restrictions of ecological research to `office hours` (08.00-

Plan to cull Endangered species

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

Acknowledgments

Thank you for your attention

The organisers of the workshop for inviting me to present today in particular Ehsan Dulloo, Prof.Jaufeerally-Fakim, Shelagh Kell and Nigel Maxted