An overview of biodiversity conservation in Mauritius
F. B. Vincent FLORENS
Department of Biosciences University of Mauritius Outline Introducing 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 Mauritius
~ 7.6 MY old Volcanic island ~900 km East of Madagascar Maximum altitude 828m 1865 Km2
Discovered by the Portuguese in early 16th Century Colonised: 1638 Dutch - 1722 French - 1810 British 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. Biodiversity ± Angiosperms
691 species (39.5 % endemism) Biodiversity - Birds 42 species (33% endemism) Biodiversity- Reptiles 20 species (80% endemism) Biodiversity ± Ecosystems A wealth of different ecosystems from dry coastal vegetation to wet tropical and mossy forests, marshes etc Dodo: Symbol of human-caused extinction 6WLOOFORVHWRRXUKHDUWV« 0DQ\H[WLQFWLRQVORVWRIIXQFWLRQV IUXJLYRUHVEURZVHUV«
1 Roussette Tortoises 1864 1840 Gibbus Pigeon Hollandais Tropidophora 1914 1826 carinata 1881 Grey Parrot P Schouten 1759 Burrowing boa 1974 Dodo 1700
Ren hen 1693
Raven Parrot 1674
Other paintings J Hume 0 1600 1620 1640 1660 1680 1700 1720 1740 1760 1780 1800 1820 1840 1860 1880 1900 1920 1940 1960 1980 Approximate year of extinction Extinctions rates
100
90
80
70
60
50 of extinction of 40
30
20
Pourcentage d'extinction Pourcentage 10
Percentage 0 PlantesPlants ReptilesReptiles BirdsOiseaux EscargotsSnails From bad to worst.... Habitat destruction (Major cause of extinctions) Minimum viable populations? Habitat fragmentation µ*KRVWRISDVWGHIRUHVWDWLRQ¶
Ahead of the world in terms of habitat destruction and fragmentation
(6RXUFH9DXJKDQDQG:LHKH3DJHDQG'¶$UJHQW 6RXUFH9DXJKDQDQG:LHKH3DJHDQG'¶$UJHQW Predictions rather grim
Ecosystem 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
$EDQRQKDUYHVWLQJRI³SDOPHWWRV´ZDVGHFODUHGE\+XJR in 1670 EXWQRWHQIRUFHG« Alien species* Plants (23 serious Animals invader species)
Psidium cattleianum
Feral pig Macaque«.
Lantana camara
* 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 plants Understorey heavily dominated by alien plants
11000 Native 10000 Natives Aliens Alien 9000 SORWVRIPðIURPVLWHVZLWKµEHVWSUHVHUYHG¶IRUHVWV) 8000
7000
6000
5000
4000
3000
Number of individuals
2000
1000
0 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) Alien plant invasion progress over 20 years
> 2.5 cm Sites Lorence & This study dbh Sussman ¶V % alien Brise Fer 20.8 27.5 Ï plants Bel Ombre 34.8 60.7 Ï
Native Brise Fer 49 42 7.4 n.s. species Bel Ombre 56 55 7.7 n.s. richness Native Brise Fer 76.2 58 9.1 Ð density Bel Ombre 71.5 63 11.2 Ð (1000 m2) Acute conservation FKDOOHQJHV« Many species on the brink, including CWR
Pandanus pseudomontanus
Hyophorbe amaricaulis Rarest screwpine in the world Rarest species worldwide
Dombeya mauritiana 1 survivor in the wild Conservation Management Areas
All invasive alien plants weeded
Fenced to exclude alien pigs (Sus scrofa) and Java deer (Rusa timorensis) Effect of weeding on woody plants Results: Individual and population level (Sideroxylon grandiflorum ± Tambalacoque) Reproductive output (S. grandiflorum ± µ'RGRWUHH¶
Invasion strongly reduces reproductive output
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 Growth and mortality of Sideroxylon grandiflorum
Higher growth rate in managed (weeded) sites
Mean growth rate/year Site N (cm ± 95%CI)
Non-weeded 125 0.046 ± 0.046
Weeded 155 0.112 ± 0.042
Higher mortality rate on invaded forests
Site N Mean mortality/year
Non-weeded 140 13 2.7%
Weeded 160 1 0.16% Mean growth rate of all woody native species
Non weeded Weeded
Average Average Number (dbh, mm) -95% 95% Number (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 Weeded Not weeded
500 500 2003 450 450 400 400 2007 350 350 300 300 250 250 200 200 150 150
100 100 Brise Brise Fer 50 50 0 0 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10 to 15 to > 20 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10 to 15 to > 20 15 20 15 20
500 500 450 450 400 400 350 350 300 300 250 250 200 200 Number Number of individuals 150 150 100 100 50 50 0 0 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10 to 15 to > 20 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10 to 15 to > 20 MareLongue 15 20 15 20 DBH class (cm) Invasion effect on native Cyathea spp. (tree ferns) Comparison between 1 ha invaded and 1 ha weeded
(Thormann, Baider & Florens unpubl data)
350 Adult 318 Juvenile 300
250
200
150
Individuals/ha 100
50 3 0 0 0 Managed Invaded Large epiphyticInvasion ferns effect on native Cyathea spp. (tree ferns) Comparison between 1 ha invaded and 1 ha weeded
(Thormann, Baider & Florens unpubl data)
350 Adult 318 Juvenile 300
250
200
150
Individuals/ha 100
50 3 0 0 0 (Bindewald, Baider &Managed Florens unpubl) Invaded Population recovery within 24 years
180 Kruskal-Wallis test: H = 154.49; p < 0.001 {0.1ha plots} b 160
140
per ha per 120 Asplenium nidus 100
Asplenium nidus Asplenium 80
60
40
Density adult of 20 a a
0 250 Kruskal-WallisNon-weeded test: Weeded 1996 Weeded 1986 H = 122.73; p < 0.001 {0.1ha plots} b
per ha per 200 Microsorum
150
100
Microsorum punctatum Microsorum a
50 a
Density adult of
0 Non-weeded Weeded 1996 Weeded 1986
Butterflies: Species richness
12.5 Alien-invaded forest 11.5 ) Non-invaded forest 10.5 Tau - 9.5 Mao
( 8.5
7.5
6.5
5.5
4.5
3.5
2.5
1.5
0.5 Estimated species species richness Estimated -0.5 1 5 9 13 17 21 25 29 33 37 41 Cumulative number of transects
Florens et al 2010. Biodiversity and Conservation Butterfly: Abundance Average density of butterfly per transect
Sites Weeded Non-weeded forest forest Bel Ombre (Bellouguet) 6.75 0 Bel Ombre (Fixon) 4.5 0.17 %ULVH)HU µ2OG3ORW¶ 6 0.17 %ULVH)HU µ5DOHLJK3ORW¶ 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
Florens et al 2010. Biodiversity and Conservation Abundance of birds Method: Fixed radius point counts, with a radius of 20 m (Hostetler & Main, 2008)
Namah, Baider & Florens unpubl Exclusion fencing as conservation measure
Fenced to exclude alien pigs (Sus scrofa) and Java deer (Rusa timorensis) )HQFLQJDVVXPHGWRZRUN«%XWGLGQRW Influence of pig and deer exclosures 250 Mare Longue Weeded + Fenced 200 Exclosure + alien plants weeding
150
Alien guava fruiting Not weeded + Not fenced 100 season No exclosure, no weeding.
Number of 'live' artificial seedling artificial 'live' of Number 50 Exclosures are ineffective in 0 controlling trampling / 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 10/1/05 10/2/05 10/3/05 10/11/0310/12/03 10/10/0410/11/0410/12/04 250 Brise Fer uprooting damage by large alien mammals 200
NotNo weeded exclosure, + Not no fenced weeding Seedling numberSeedling 150 Alien guava fruiting 100 season NotExclosure weeded + only Fenced
Number of 'live' artificial seedling artificial 'live' of Number 50
0
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 18/1/05 18/2/05 18/12/03 Date 18/10/04 18/11/04 18/12/04 Alien rats Rattus rattus and R. norvegicus
Seed predation
Canarium - Burseraceae Mimusops - Sapotaceae Predator control
Trap (Macaque) Traps (rat, mongooseFDW«
Poison stations (rat) Predator control: e.g. Hare and rat
$OLHQPDPPDOHUDGLFDWLRQIURPDQRIIVKRUHLVOHW *XQQHU¶V4XRLQ µVSHFWDFXODU¶UHFRYHU\
1500 1982 1350 1993 1200 Hare and rat eradication 2004 1050
900
750
600 Pandanus vandermeeschii Pandanus 450
300
150 Frequency of of Frequency 0 Seedlings and non- Reproductive trees Dead adult trees Screwpine (Pandanus reprodutive trees vandermeeschii) Re-introduction/augmentation programs Mauritius is well known for some conservation successes« < 30 birds 4 birds 18 birds
Now 600 Now 440 Now 450
Captive breeding
Re-introduction
Artificial nests (nest boxes)
Supplementary feeding
Predator control Land tortoise analogue species
2008 2002
2010 Restoration sites
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
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)
µ9LHWQDP¶ (1995)
µ9LHWQDP¶ (+ 15 years) 30 U14,14 = 7.5; p < 0.0001 25
20 Min-Max saplings per plot per saplings 25%-75% a 15 n a Median value g n u 10 r a
H 5 0
Number of Before After
14 12 10 8 6 4 2 0
a a s s a a a a a s a s a a a i i a i a a a i n i e t e e i a e r r e e p o l d x g e e f l n o i c m o i s f r l l u p e h a o k a a s s f u e e L y n e n r s o y i e h r L n i n c d g a N t i n p x a p i V t l u e C n d O r s d o i r n n C n H A e o m o u r t u r o n A i i r e a T n c M a a o d A e G M D i d H S W S r u o b a
Mean growth rate in trunk girth (mm/yr) L
Recent policies
Government policy: restrictions of ecological research to `office hours` (08.00- « Plan to cull Endangered species Conclusions
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
1. Control of invasive alien plants
2. Control and eradication of invasive alien animals
3. Population reintroduction/augmentation or analogue introduction Conclusions
Many 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
The organisers of the workshop for inviting me to present today in particular Ehsan Dulloo, Prof.Jaufeerally-Fakim, Shelagh Kell and Nigel Maxted
Thank you for your attention