Endangered Endemic Fauna and Flora of the Indian Ocean Island of Mauritius

THE MASCARENE ISLANDS BIOMES AND ECOSYSTEMS Endangered Endemic Fauna and Flora of the Indian Ocean Island of Mauritius Dr. R. Venkatasamy Consultant EnviroSolutions Ltd Mauritius Summary: Oceanic islands ecosystems are unique in that most islands remained uninhabited for a long time, and fauna and flora species evolved undisturbed and very differently from continental species. However, the advent of human settlements and introduction of exotic species quickly caused irreparable damage to fragile island ecosystems, leading to the extinction of many interesting and rare species, as has been the case with endemic fauna and flora species that existed on the Indian Ocean island of Mauritius. The Mascarene Islands and Island Ecosystems The Mascarene group of Islands form a distinct eco region which contains habitats and species that differ from their assigned biome. Originally, these islands were covered with tropical moist broadleaf forests, habitat to a diverse range of fauna and flora. The common transition included coastal wetlands and swamp forests near seacoasts, windward rain forest, leeward lowland dry forest, to palm savannas, montane deciduous forests, and sometimes montane heathlands on high peaks. Figure1: The Mascarene Islands Prior to the coming of settlers, these islands were home to many unique endemic plants and animals, assumed to be originally derived from nearby Madagascar and the East African coastal countries. However, these islands have never been connected to either Madagascar or mainland Africa. Consequently, one different theory is that the flora and fauna of the Mascarenes must have either arrived from over the sea, or used other islands of the original Mascarene Plateau, now disappeared under the sea, as 'stepping stones' to hop from one land mass to another. The uniqueness of the Mascarene islands is in that they form systems in which biological diversity varies as a consequence of remoteness and size, but not necessarily because of environmental factors. On the whole, they are generally simpler systems than conventional continental ecosystems and biomes. Islands may thus provide an opportunity to determine how island biological diversity may affect ecosystem functions. Islands have been known to present two specific paradoxes: Diversity, and Stability. 1

Although being highly species-poor, existing species have represented considerable biological interest in terms of unusual endemic genera and taxonomically isolated groups. They have enjoyed stability, as they have persisted for millions of years through whatever adverse or extreme climatic events they may have had to face. However, once exposed to extrinsic (anthropogenic) disturbances, they quickly lose that stability. These apparent paradoxes are resolved when it is realized that all these features are consequences of the same island characteristics: Biotic isolation, and Oceanicity. As a result of these two characteristics, island systems are quantitatively and qualitatively different from continental systems in the nature of their ecological processes, which appear to give rise to an interspersed equilibrium model of evolutionary change. Rare and unique island endemics may be either the remnants of ancient continental endemics displaying prolonged stasis and persistence, or products of adaptation and evolution of localised species representing a series of rapid but irreversible events. A process-based definition of a relict endemic (palaeoendemic) is one whose founding lineage (i.e. the original continental source taxon) having left no descendents on the continent of origin, or the continental lineage may have evolved into totally different forms. The time of separation between an island endemic and its continental sister-group should predate the colonization of the island by the now endemic lineage. These island relict endemics are important representatives of remnants of the last segments of biodiversity that have vanished from continental ecosystems. For island conservation strategies to be successful, an integrated understanding of both sides of the diversity and stability paradox needs to be understood and appreciated so that both island processes and island organisms can be conserved. Oceans of the world have isolated volcanic islands, generally formed from hotspot activities underlying the ocean s crust. The character of the terrestrial biota of these islands cannot be dependant on the ocean, but rather on whichever source continent has ultimately been responsible for providing the colonists. The African continent provides a good example, as it is surrounded by many small islands, including Reunion, Mauritius and Rodrigues, forming part of the Mascarenes. These islands may have sampled the African biota from different geological times, preserved it, and re-invented some through normal processes of evolution. Each island has its particular biota due to age, size, geographical isolation and such other factors as climate and exposure. A number of factors have to be considered when examining island ecosystems, including: Components responsible for biological diversity on islands and their patterns of variation, Threats and risks in maintaining such biological diversity, Intricacies of island biology and consequences of modifications by men over ecosystem functions, The global necessity for islands biodiversity studies in conservation, and How we can learn from islands in understanding the processes that induce changes on continental ecosystems. It is known that introduced (exotic) species have better chances of survival on island environments than on mainland areas, and have been shown to have greater negative impacts there, since island ecosystems are known to be fragile, and island species weak. Island species have been termed, wrongly or rightly, backwaters and deadends, whereas island ecosystems 2

are seen as presenting less biotic resistance to invaders or introduced exotic species than do continental ecosystems. However, genetic weaknesses in island species, if any, are debatable. Island endemic species have evolved in isolation, and it is expected that natural selection would have adapted them better to their environment than invasive or introduced species. But that has not been the case. The percentage of introduced species (not to be confused with invasion) has always been higher on isolated, uninhabited islands than on continental masses,. Many islands have been regarded as ideal environments for the introduction of exotic species, partly to enrich the less dense populations of endemic species, or to provide sources of sustenance for settlers. Though island species are not basically unadaptative weaklings, there exist an aspect of island biota that predisposes them to be particularly susceptible to introduced species, especially predators of the aggressive, competing and scavenging types, since most island environments have lacked such predators. As a consequence, native species evolved without any need to fend off predators, or develop specific defensive or aggressive strategies. The absence of such characteristics, not necessarily their weaknesses, was often the cause for their decimation and rapid extinction. Another factor that predisposes island native communities to be vulnerable lies in the fact that islands have smaller surface areas than continents, and it is unlikely that space occupied by native species would have enough room for introduced species that will compete for food, nesting spaces, and territories. Other factors that have also contributed to the disappearance of native species include hurricanes, fire, and sometimes, changes in climatic conditions. But species lost through these agents must have been few. The dodos of Mauritius must have survived innumerable hurricanes and other factors adverse to life, but only disappeared when human colonisers, together with exotic species and predators, landed on the island. There is ample evidence that species extinction inexorably followed the advent of human colonisation of islands, and that is well documented. The disappearance of the Dodo on the island of Mauritius, and the rapid extinction of the Moa bird in New Zealand are two of the many instances where human colonisation has led to rapid disappearance of fauna and flora on islands. Several reasons have been attributed to this human-induced extinction: Human colonisers/settlers were more interested in valuable timber species, clearfelling large areas, at the same time destroying habitats of native endemic species. Settlers on newly colonised islands soon started clearing forests and shrubland for agricultural purposes, further destroying habitats. Settlers brought with them domestic animals, some of them known predators, and farm animals, and both further engaged into habitat destruction and species reductions. Settlers introduced new exotic species that may have been useful to them in several ways, but increasing competition with and aggression to native species. Settlers themselves turned into predators, hunting local species for food, skins, plumage, or for exportation. The Island of Mauritius Location The island of Mauritius lies about 800 kilometres East of Madagascar between longitudes 57 18' and 57 49' East, and latitudes 19 59' and 20 32' South. It is sixty-one kilometres long and fortysix kilometres wide at the extremes and has a total land area of some 1,865 square kilometres. 3

Figure 2: Mauritius - Location Mauritius is believed to be the oldest of the Mascarene Islands followed by Réunion and Rodrigues islands. The oldest rocks of these islands have been dated at ca. 8 million, 3 million and 1.5 million years old respectively. However, there is still much debate about the age of Rodrigues, many believing it to be the oldest of the islands, based on its geology, biogeography and palaeontology. Climate Temperatures along the coast are warm and seasonal, in summer (December-April) averaging 30 C, while in winter (May-November) the average is closer to 25 C. At higher elevations and mountain peaks the temperature is cooler, averaging 18 C. The prevailing winds are the South- Easterly trades, which blow throughout the year. In the lowlands of Mauritius, the rainfall varies from 890 mm on the leeward side of the island, to 1905 mm on the Southeast coast. In the uplands, the rainfall varies from 2540 mm to 4445 mm per annum. The rainfall is sufficient to permit the development of tropical moist forest on the windward side of the island and tropical dry forest on the leeward side. Tropical cyclones or hurricanes can be frequent, and may have influenced species assemblages on the island. History For a long time unknown and uninhabited, the island was probably first visited by Arab sailors during the Middle Ages. The Portuguese sailor Domingo Fernandez Pereira is known to be the first European to land on the island at around 1511, appearing as `Cirne' on early Portuguese maps, possibly because of the presence of the Dodo, described by the Portuguese as a flightless bird that was found in great numbers at that time. Subsequently, Pedro Mascarenhas, a Portuguese explorer, arrived on the shores of Mauritius in 1512 with European settlers, together with pigs, goats, chickens, dogs, cats and rats, being some of the first exotic animals to be introduced by early settlers. Both settlers and introduced species contributed to dramatic changes in the ecology of the island, resulting in a substantial reduction in the number of endemic species. It was Pedro Mascarenhas, who gave the name Mascarenes to the group of islands now known as Mauritius, Rodrigues and Reunion. However, the Portuguese did not stay long as they were not interested in these islands, but they did leave their introduced exotic species behind, to continue modifying the natural environment, causing havoc to native species. Colonisation proper began at around 1598 with the Dutch, and the island was renamed Mauritius, in honour of Prince Maurice Van Nassau, "Stathouder" of Holland. They brought 4

with them slaves from Africa, deer from java, wild boars, black rats, cats, dogs, the mongoose, monkeys, tobacco and sugar cane, to name a few. It was during this period of intensive farming and exploitation of forest resources that the dodo vanished forever, through hunting by humans and introduced carnivores, and destruction of their natural habitats. However, the first Dutch settlement lasted only twenty years. Several attempts were subsequently made, but the settlements never developed enough to be successful and permanent, and the Dutch finally left Mauritius in 1710, after having caused considerable damage to the island s natural ecosystem, and its endemic species. In 1715 the French claimed the island renaming it Ile de France, and the processes of introduction of exotic species and exploitation of the natural hardwood forests accelerated, together with intensified clearing of native forest and shrub land for agriculture, mainly sugar cane plantations. In 1810 it became British, and under the auspices of the East India Company trading and agriculture flourished, with further introduction of exotic species of fauna and flora, and further destruction of native ecosystems and habitats. The pressure on the ebony forests continued, and the expansion of the sugar cane industry accelerated deforestation. The situation has not been different in recent years. Population growth, demand for land for agricultural activities, replacement of hardwood forests and scrubs with fast growing exotic species for timber production, and use of pesticides to eradicate insects, including small mammals (the food source for a number of the endemic fauna species), negatively affecting endemic fauna species Fauna and Flora The first Dutch sailors who landed on Mauritius described the island as being mountainous and misty, covered in dense forests full of beautiful trees, with many fresh water rivers and especially an abundance of food. The profusion of birds and marine species was described in great detail and they mentioned of catching so many big birds by hand that they could not eat all, and pointed out that they could have caught many more since the birds were so docile. Turtles, fish, rays and eels were plentiful and regularly on the menu. Before they left, they left behind exotic plants they had grown and some of the animals they had brought. That was the beginning of Man s destructive activity here, and four centuries later, nothing of the previous natural abundance mentioned is left. The succession of colonizing settlements that followed massively destroyed the endemic fauna and flora and introduced various exotic species of plants and animals, of which many proved to be highly invasive and uncontrollable. What can be said about the first people that colonized Mauritius is that they knew nothing of the consequences of their acts. Biodiversity is the variety of life at all levels of biological organization, and Mauritius has a diverse fauna and flora that has evolved over millions of years to produce very distinct forms of plants and animals unique to the island and existing nowhere else on earth. These species are said to be endemic to the island as they have special characteristics and traits that distinguish them from earlier ancestors. Today, there is less than 2% left of the original native forest which once used to cover the island, Deforestation, over exploitation of native species, introduction of invasive exotic species and intensive mono-agricultural developments such as the cultivation of sugar cane coupled with a massive population boom have reduced the island s biodiversity to a frighteningly fragile state. The flora of Mauritius is diverse containing as many as 700 different species of ferns and flowering plants. Among these varieties of plants and flowers, 311 species belong to the Mascarene Islands and 45% is indigenous to the island of Mauritius. Almost 150 species of native Mauritius flora are presently on the list of critically endangered species. Due to the presence of a vast range of uncommon animals and plants, the flora and fauna in Mauritius is 5

under tremendous pressure. Serious problems regarding the regeneration of the plants are surfacing, as many unwanted species of plants tend to chock the existing native varieties. The upland areas of forest that now remain are almost entirely invaded by exotic species of flora and fauna, degrading the ecosystems beyond the point from which they can either regenerate or reproduce without intense management strategies. Out of the 311 endemic plant species on the island, 113 are classified as endangered. 50 of the 113 species are threatened, being represented by less than 10 in the wild. Some endemic genera include species of Ramosmania, Nesocodon, Cylindrocline, Roussea, Tectiphiala, Doricera, Hornea, Trochetia boutoniana (the national flower), Pittosporum, Diospyros spp., Tambourissa, Hibiscus, and Latania, to mention a few. The fauna species of Mauritius have suffered through the influences of human settlers and introduced exotic species in the same way. Of the 3 fruit-eating bat species only one has survived extinction (Pteropus niger), and now a protected mammal. There are also two species of insectivorous bats, the tomb bat (Taphozux mauritianus), and the Natal free-tail bat (Mormopterus acetabulosus) that are under threat. Surviving endemic reptiles are all under threat, and include: the Round Island burrowing boa (Bolyeria multocarinata), the Round Island Keel-scaled boa (Casarea dussumieri), the Mauritius blindsnake (Typhlops cariei), the Lesser night gecko (Nactus coindemirensis), the Serpent Island night gecko (Nactus serpensinsula), the blue-tailed day gecko (Phelsuma cepediana), the Round Island day gecko (Phelsuma guentheri), the Mauritius forest day gecko (Phelsuma guimbeaui), the Ornate day gecko (Phelsuma ornate), Bojer's Skink (Gongylomorphus bojerii), the Mauritius giant skink (Leiolopisma mauritiana), and the Round Island skink (Leiolopisma telfairii). The two species of giant tortoise that used to be found on the island, the saddle-backed Mauritius gian tortoise (Cylindraspis inepta), and the domed Mauritius giant tortoise (Cylindraspis triserrata) are now both extinct. The list of extinct birds is quite long for a small island, and includes: the dodo (Raphus cucullatus), the blue Pigeon (Alectroenas nitidissima), the broad-billed parrot (Lophopsittacus mauritianus), the grey parrot (Psittacula bensoni), the Mascarene coot (Fulica newtonii), the Mauritian duck (Anas theodori), the Mauritian shelduck (Alopochen mauritianus), the Mauritian owl (Mascarenotus sauzieri/ Strix sauzieri), the Mascarene swan (Sarcidiornis mauritania) the Mauritius night heron (Nycticorax mauritianus), the red rail (Aphanapteryx bonasia), the Bourbon crested starling(fregilupus varius), and several others that have been identified and named from remnants of bones collected. Those that have barely managed to survive, classified as endangered and under intensive conservation include: the echo parakeet (Psittacula echo), the kestrel (Falco punctatus), the pink pigeon (Nesoenas mayeri), the Mauritius fody (Foudia rubra), the paradise flycatcher (Terpsiphone bourbonniensis desolata), the cuckoo shrike (Coracina typical), the grey white eye (Zosterops borbonicus mauritianus), the olive white eye (Zosterops chloronothus), and the black bulbul (Hypsipetes olivaceus). Causes of extinction Extinction is a natural event and often routine from a geological point of view. Most of the species that originally lived on our planet are now gone extinct. The average rate over the past 200 million years has been between 1-2 species per year, and 3-4 families per million years. The average duration of a species is 2-10 million years (based on the last 200 million years). There 6

have also been occasional episodes of mass extinction, when many taxa representing a wide array of species have gone extinct. Today, due to human actions, species and ecosystems are threatened with destruction to an extent rarely seen in the history of our planet, and these are attributed to many causes, including: A growing human population with resulting human activities. Over-hunting Over-harvesting. Habitat loss, habitat degradation, and habitat fragmentation. Invasion by non-native species. Pollution and contamination. Climate change. Conservation policies and strategies The most effective long-term response to preserve endemic fauna and flora populations is to protect their habitats and to manage threatened species in those habitats. However, for many species this response cannot be implemented quickly enough to prevent extinction. For this reason, conservation activities necessarily extend beyond in situ habitat management to incorporate a coordinated strategy that integrates conservation with education, scientific research, and propagation of at-risk species in situ and ex situ. Mauritius has ratified the Convention on Biological Diversity, and has initiated national biodiversity strategic action plans and developed national nature reserves and protected areas for both fauna and flora. The achievements of the targets set by the international community in relevant international conventions are of particular importance to Mauritius, and to achieve those targets in the agreed time frames, the following actions are necessary: Integrating biodiversity protection into national sustainable development strategies; Addressing biodiversity in a manner that responds to the unique characteristics of the island s endemic fauna and flora; Enhancing national efforts, in the establishment of protected areas consistent with international law and based on scientific information; Controlling invasive species; Developing strategic plans for the protection and conservation of endangered endemic flora and fauna; Establishing the necessary institutions for the protection and conservation of endemic flora and fauna; Establishing the necessary research facilities for developing conservation methodologies for the protection and propagation of endemic flora and fauna. Further Reading Wilson, E.O. 1992. The Diversity of Life. W.W. Norton & Co., New York Quammen, David. 1997. The Song of the Dodo: Island Biogeography in an Age of Extinctions. Simon & Schuster, New York. Barnwell, P. J. and Auguste Toussaint. 1949. A short history of Mauritius. Longmans-Green, London. BirdLife International. 2000. Threatened birds of the world. Lynx Edicions, Barcelona, Spain, and BirdLife International, Cambridge, UK. Carter, S.P. and P.W Bright. 2002. Habitat refuges as alternatives to predator control for the conservation of endangered Mauritian birds. In: Veitch, C.R. and Clout, M.N. (Eds) Turning the Tide: The Eradication of Invasive Species. Proceedings of the International Conference on Eradication of Island Invasives. IUCN, Gland, Switzerland. 7

Cheke, A. S. 1987a. An ecological history of the Mascarene Islands, with particular reference to extinctions and introductions of land vertebrates. Pp. 5 89 in A. W. Diamond, ed. Studies of Mascarene island birds. Cambridge, UK: Cambridge University Press CITES. http://www.cites.org Collar, N.J., and S.N. Stuart (eds.). 1985. Threatened birds of Africa and related islands: the ICBP/IUCN Red Data Book, Part 1. 3rd ed. International Council for Bird Preservation, Cambridge, UK. Durrell Wildlife Conservation Trust. http://www.durrell.org/animals/birds/echo-parakeet/ IUCN Red List. http://www.iucnredlist.org Jones, C. G. 1996. Bird introductions to Mauritius: status and relationships with native birds. In: The introduction and naturalisation of birds, J. S. Holmes and J. R. Simons (eds.). HMSO, London, UK, pp. 113 123. Mauritian Wildlife Foundation. http://www.mauritianwildlife.org/article.php?cat=projects&title=01.%20mauritius%20kestrel Sinclair, I. and O. Langrand. 2004. Birds of the Indian Ocean Islands: Madagascar, Mauritius, Seychelles, Reunion and the Comoros. Struik, Cape Town. S. Africa Staub, F. 1976. Birds of the Mascarenes and Saint Brandon. LABAMA HOUSE, Port Louis, Mauritius. Staub, F. 1993. Fauna of Mauritius and associated flora. Précigraph Limited, Port Louis, Mauritius. Toussaint Auguste. 1971. Histoire de l'île Maurice, éd. PUF, France Dr Ramakrishna Venkatasamy <venkatasamyr@yahoo.com> Environmental consultant and scholar Mauritius 25/07/2016 8