UCT conservation expertise takes root on La Réunion

Conservation partnership: UCT's Assoc Prof Dave Richardson (right) and postdoctoral fellow Mathieu Rouget, have worked to put together a conservation plan for the Indian Ocean island, La Réunion, at the behest of the French government and with funding from the NRF and French sources.

With funding from the National Research Foundation and the French Ministry of Foreign Affairs, UCT and French researchers have collaborated to devise a conservation plan for the Indian Ocean island of La Réunion's rich plant species. This knowledge transfer paves the way for similar initiatives elsewhere on the sub-continent.

Across the broad expanse of the Indian Ocean, skipping the bulk of Madagascar, is the volcanic isle of La Réunion - rugged and isolated and one of the world's 25 biodiversity hotspots. But until recently it was an island without a conservation plan.

The island's authorities were also under considerable pressure by the French government (La Réunion is one of 14 French regions) to identify suitable areas for national parks and other protected areas.

This resulted in an interesting collaboration between UCT and French researchers via an agreement co-financed by South Africa's National Research Foundation (NRF) and the French Ministry of Foreign Affairs, working with the University of La Réunion. Their brief? To devise a plan to conserve the island's special biota with its rich variety of endemic plant and animal species.

Two UCT researchers were pulled in to tackle the task: Associate Professor Dave Richardson and postdoctoral fellow Mathieu Rouget. The duo used an approach for conservation planning developed by UCT's Institute for Plant Conservation for the Cape Floristic Region. The plan identifies broad habitat units as biodiversity entities for systematic conservation planning.

The researchers' study is the first spatially explicit assessment of habitat diversity and transformation in La Réunion.

"Sophisticated techniques were needed to assess the status of protection of the island's unique habitats," said Richardson, who is also deputy director of the institute.

Rouget, fortuitously, graduated from the University of La Réunion and his mother-tongue skills and knowledge of the island have been especially valuable to the project.

Richardson and Rouget have also worked closely with ecologist Dominique Strasberg, deputy dean of research at Réunion University's science faculty.

Lying on the submarine Mascarene Plateau, La Réunion is one of three islands that make up the Mascarene Islands, east of Madagascar. (The others are Rodrigues and Mauritius.) The islands were apparently known to Arab traders but were officially discovered by the Portuguese at the beginning of the sixth century. They were named after Pedros Mascarentas, who visited these pinpricks of land in the vast Indian Ocean in 1512.

Unlike Mauritius, La Réunion is a volcanic island dominated by two large peaks, one of which is Piton de la Fournaise, one of the world's most active volcanoes. It is home to an eclectic mix of people, including Indians, Chinese and French-speaking Europeans.

These islands are unique, and due to their isolation, possess many endemic species. But the effects of hunting, species introductions, deforestation, farming and urbanisation have dramatically changed the habitats and caused the extinction of species. Many surviving endemic Mascarene species are seriously threatened.

As with all islands, La Réunion faces many threats, including severe and rapidly escalating impacts due to invasive alien species. A reported 30 out of 45 native terrestrial vertebrates have become extinct since European occupation of the island.

The flora, originally comprising 500 native species, is now dominated by 2 000 introduced species of which about 628 are naturalised and 62 highly invasive.

"La Réunion is by far the most intact habitat of the three Mascarene Islands, but its natural habitats are under siege from urbanisation, agriculture and alien plant invasions," Richardson explained. And although La Réunion has no formal conservation areas, it has by far the largest area of relatively intact habitat of the Mascarene islands. This is largely due to its rugged topography, which has precluded agriculture and other forms of land use in some habitats.

"But the opportunities for preserving tracts of Mascarene ecosystems on La Réunion are very good," Richardson added. Most importantly, with a proper network of conserved areas, La Réunion could also serve as a benchmark for restoration of habitats on other south western Indian Ocean Islands, he said.

Richardson and Rouget began their work with mandatory consultations in the capital of Saint Denis, where they hosted a number of workshops and meetings with interested and affected parties.

But they faced a number of hurdles. Details and maps of the islands were sparse. Their first task was to produce a map of the island dividing it into manageable habitats. As little information was available on the island's former natural state, they revisited important vegetation studies, including the 1970s findings of Frenchman Theresien Cadet, who had produced an island-wide description of vegetation types

With a broad idea of the vegetation types the island supported, they used data on altitude, soil types, rainfall and climate and their association with vegetation types, to reconstruct the original (pre-transformation) extent of natural habitats.

This information was entered into a Geographical Information System (GIS) and enabled the researchers to map coarse-filter biodiversity surrogates and to identify areas where the habitat had been transformed over the years.

"We proposed a protocol for defining a system of habitats and for using these to provide a preliminary assessment of conservation priorities for La Réunion," Richardson elaborated. "The protocol draws on existing data and expert knowledge to map habitat types, assesses the extent of habitat transformation, and quantifies heterogeneity between habitat types.

"Importantly, this approach can be duplicated for conservation plans on the other two Mascarene Islands, where similar levels of information are available."

In their studies, the researchers found that the island's pattern of habitat transformation was uneven among the 19 habitat types identified.

"While three habitats have lost 95% of their original area, four still have 80% of their original extent," Richardson said.

These habitat types fall into the following categories:

• Transformed habitats, mostly with low levels of plant endemism
• Habitats confined to homogenous geology, usually with high levels of plant endemism, and
• Species-rich heterogeneous habitats on diverse geological types.

"Urgent action is needed for several habitat types that are restricted to a few municipalities and/or where a large part of the original extent has been transformed."

In particular, three habitat types (Subalpine Sophora thicket, Mesic submountain forest and Philippia thicket) emerged as conservation priorities.

But several factors hinder conservation: poor stakeholder commitment and a lack of maps of island-wide biodiversity features.

Added to these factors is growing urbanisation. The population on the 2 512km2 island is set to reach one million by 2020. Almost 50% of the island has been transformed by crops and urban area or is now covered by secondary vegetation.

As the island is divided into and managed by 24 municipalities (these range in size from 16 to 241km2), these authorities were identified as a basis for implementing conservation priorities.

"Firstly, the municipalities are responsible for decision-making regarding land use, especially urban expansion. Secondly, municipalities in La Réunion are relatively homogenous in size and each has a coastal and montane section. Thirdly, their boundaries follow on major topographic features such as cirques, cliffs and waterways," Rouget explained.

Various criteria were used for assessing habitats for conservation. "We considered the frequency of each habitat type among the 24 municipal zones to quantify vulnerability," Richardson said. "Thus a habitat occurring in few municipal zones is more likely to be lost through agricultural or urban expansion than one occurring in more municipal zones. This way we identified municipal zones where priority habitats occur."

One habitat, the lowland savanna, has almost gone and only a few individual trees remain. Two others, the lowland dry forest and the subalpine Sophora thicket, have less than 1% of their original distribution intact. Only two habitats remain unaffected by invasion: the Pandanus mountain wet thicket and the subalpine shrubland, high up on the mountains.

Some habitat types, such as the subalpine herbland, are largely invaded but not transformed while others, such as Philippia mountain thicket, have been transformed but fortunately not invaded. La Réunion is also the last of the Mascarene Islands with large areas of untransformed forest; and these thus represent regional conservation priorities.

And although the island's habitats are under threat from tourism and urban development, Richardson and Rouget are confident that La Réunion has the opportunity to preserve a representative sample of all habitat types. Maps from their broad-scale analysis of habitat diversity are already in use by local stakeholders in land management and conservation.

"The project has paved the way for more detailed conservation planning and hopefully the creation of formal networks of reserves and other conservation initiatives," Richardson added.

Local decision makers are also currently implementing a national park project with the support of the French Minsitère de l' Environne-ment.

"In the old days it was thought to be sufficient to keep a certain percentage of land for reserves. It's now evident that we need to conserve representative parts of all habitats, with an emphasis on connectedness," Richardson said.

"It's been very encouraging to see that the work we have done has been so well accepted."

But the relationship goes beyond conservation planning and back to conservation research and education. Benis Egoh, a postgraduate researcher at UCT, is currently working on La Réunion, and funds are in place for further exchange of students between UCT and La Réunion to refine aspects of the initial plan. Special emphasis will be given to improving the understanding of the dynamics of alien plant invasions.

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