Rojer, A.C.

Vegetation maps are a primary and essential tool in biodiversity science, conservation, management, and monitoring as well as in land-use management planning. In this study a semi-detailed landscape-based vegetation map (scale: 1: 46,000) is presented for the 34 km2 Dutch half of Lesser Antillean island of St. Martin (St. Maarten). A vegetation map is especially critical in biodiversity context as St. Maarten lies in a key biodiversity hot spot and is habitat to more than 100 regional endemic animal and plant species of which 12 are island endemic species found only on St. Maarten. The map is based on a total of 56 vegetation plots that were sampled in 1999 using a stratified random sampling design and analysed using TWINSPAN cluster analysis. Two hundred and twenty (220) plant species, representing 40 % of the total known flora (544 species), were recorded in the sample plots.

A total of four main and eleven different sub-landscape types were distinguished based on geology, geomorphology and the eleven distinguished vegetation types. The most dominant landscape type was the hilly landscape type for which seven sub-landscapes were distinguished. The 11 vegetation units we describe represent an important decline from the 16 vegetation types distinguished by STOFFERS (1956). Large changes have clearly occurred in the coverage and composition of the vegetation types of the island. Between the early 1950s and 1999 the total coverage of vegetated areas in St. Maarten declined from 67% to 42% representing a loss of 25% of the total vegetated surface of St. Maarten. Five of the vegetation units of STOFFERS (1956) have disappeared beyond recognition. These are: Hippomane woodland, Vegetation of the salt flats, Strand scrub community, Littoral woodland and Vegetation of the rock pavement. While Hippomane woodland has in part likely been lost due to hurricane impacts, most vegetation loss and degradation has been due to massive urbanization and touristic development especially in the lower and coastal parts of the island. As a consequence the vegetation types of the higher and steeper sections of the island have remained among the least disturbed and degraded. Some vegetation units described by STOFFERS (1956) have also disappeared due to actual vegetation regeneration and succession to a more diverse state due to the decline in agriculture and livestock grazing. Goat grazing remains especially high in two of the eleven vegetation types we described (50 – 80 % presence of dung in the study plots). The highest goat presence was recorded in a “new” vegetation unit (type 6) that has developed based on the domination of the invasive plants Leucaena leucocephala (jumbie bean, lead tree) and Antigonon leptopus (coral vine). 

The main threats to the vegetation of St. Maarten we discern based on this mapping project are 1) the massive scale of urbanization and touristic development the island has undergone, 2) continued uncontrolled livestock grazing, 3) invasive plant species, and 4) hurricane impacts. Unless actions are taken to stem the loss of and help restore natural vegetations, we predict that the island will continue to lose its plant diversity, and along with it the fauna which depends on that vegetation. Continued loss of natural vegetation will further exacerbate erosion, loss of freshwater, soil quality and 5 environmental resilience to climate change, as well as sedimentation in the marine environment and the concomitant loss of shallow marine habitats like seagrass beds and coral reefs.

To help prevent this scenario from developing further, we recommend several practical measures: 1) implement land-use planning and designate protected areas to preserve the native flora and fauna, 2) limit and control roaming livestock, 3) legally protect endangered and ecologically critical plant species, 4) connect protected areas by means of ecological corridors, 5) implement measures to control and limit invasive species and 6) implement long-term vegetation monitoring

The lands of the former Bolivia Plantation amount to about three-thousand three-hundred (3,300) hectares of wildlands and basically constitute the eastern quadrant of the island of Bonaire, stretching along the central east coast from Lagun  to Boka Olivia. A brief biological inventory of Bolivia was conducted  3-6 November 1997, in which semiquantitative data was collected on the terrestrial flora and fauna at 34 different sites and/or transects. With exception of most of the lower limestone terrace, Bolivia was found to be well vegetated in terms of overall vegetation cover, and to possess much in the way of of scenic landscapes.

Whereas Stoffers (1956) indicated most of the Middle (limestone) Terrace areas as constituting dry evergreen vegetation, at present most dry evergreen species are virtually absent. One consequence of this finding is that the (likely) better developed dry evergreen formations on Bonaire (e.g. Colombia, Karpata, Tolo) must now be accorded a much higher conservation priority than could heretofore be realised. 

Bolivia shows extensive signs of past agricultural use and strip-mining for coral rubble. At present feral livestock (goats and donkeys) are at clearly detrimental densities, and mining activities form an immediate threat to some very rare coastal rubble vegetation.

Based on this initial assessment, several principal conservation priorities for Bolivia can be identified. These are:

1. Nesting habitat for the Bonaire Lora, along the coastal terrace edge
2. Ecologically important food sources, especially candelabra cacti concentrated in various areas
3. The cave systems of Roshikiri and Spelonk
4. Terrace edge area along the length of the coastline
5. Coastal rubble vegetation between Spelonk and Boven Bolivia
6. Brasía terrace woodland of Beneden Bolivia
7. Washikemba woodland in the souther parts of Bolivia.

On the basis of these principal conservation values and the area's greater role as ecological corridor beween the northern and souther halves of the island, an initial scetch of recommended conservation areas is presented. The results indicate that any potential development  should be concentrated in the central section of Bolivia.

Based on four years of butterfly monitoring in four contrasting natural habitats on St. Eustatius, we document large and consistent differences in the butterfly species assemblages in the different habitats and compare the butterfly assemblages of the three windward Dutch islands to those of other islands of the Lesser Antilles. Seven new species records were established for St. Eustatius, thereby updating the butterfly list to a total of 32 species. Pieridae were the most numerically abundant group of butterflies (48%), followed by Lycaenidae (26%), Hesperiidae (12%), and smaller numbers of both Heliconiinae (6%) and Charaxinae (5%). Heliconiinae and Charaxinae both showed a significant dependence on the moister, wind-sheltered habitats of the volcanic slopes and crater of the Quill, but this dependence was particularly strong for Heliconiinae. The butterfly faunas of the windward Dutch islands numbered a total of 44 species. The presence of larval host plants needed for local reproduction was confirmed for all but two species. Cluster analysis separated the butterfly faunas of these and the surrounding islands into two groups. The more speciose butterfly assemblages of Saba, St. Eustatius, and St. Martin clustered together with the those of the surrounding higher islands of Antigua, Montserrat, Nevis, and St. Kitts, while the poorer faunas of the low-lying islands of Anguilla, St. Bartholomew, and Barbuda formed a separate cluster and had a lower species richness particularly in the Heliconiinae and Charaxinae. Based on consistent effects of elevation on butterfly faunas, at both geographic scales (between areas on St. Eustatius and between islands), our results suggest that island maximum elevation is the overriding factor explaining the distribution of butterfly faunal richness in the northern Lesser Antillean islands studied.

St. Maarten is one of the islands forming the inner arc of the Lesser Antilles. It is older than Saba and St. Eustatius. The oldest rock strata date from ± 50 million years ago. The island experienced periods of uplift and descent. In the Pleistocene period it formed one island together with Anguilla and St. Barths.

St. Maarten is irregular in form because of the many bays and lagoons. Steep rocky coasts alternate with sandy beaches. The major part of the island is hilly. Three ridges can be distinguished in the north-south direction. Only the Low Lands in the west are flat. In the past St. Maarten was a plantation island, with sugarcane cultivation reaching high up into the hills. Now tourism is the main economical activity. The island has two parts: The French and the Dutch part. About 38.000 people live on St. Maarten on the Dutch side, especially in the valleys, but also more and more in the hills. Because of the high population density and tourism development a lot of nature has already been lost, and several habitats are under pressure. According to the system of Köppen the climate of Maarten falls between a savanna and monsoon climate. The island is situated in the Atlantic hurricane zone. In September 1995 St. Maarten was hit by a severe hurricane.

At least 522 wild plants are known from St. Maarten, divided in 506 seed plants and 16 ferns. Among the plants there are two island-endemic species: Calyptranthes boldinghgii en Galactia nummelaria. Both species are very rare or have possibly disappeared already. The geographical distribution of five plants is limited to just a few islands and 3.3% of the species is endemic to the Lesser Antilles and the Virgin Islands. With respect to the moss flora, only two true mosses are known, and no liverworts.

The major part of the Dutch side of St. Maarten is covered with secondary vegetation derived from either seasonal formations or dry evergreen formations. Only on the top of the hills some more or less original semi-evergreen seasonal forest is found. This type of forest has regionally become extremely rare too. Locally it includes several species that are lacking elsewhere in the island. Because of its small area this forest formation is very vulnerable. On the higher hills of the two ridges in the middle part of the island, and on the hills of the eastern ridge, a dense secondary woodland vegetation is growing, preventing erosion and with a high scenic value. Along the coast and inland waterways remains of mangrove forests and other types of coastal vegetation survive, which are of high ecological value, and also have scenic value.

The fauna of St. Maarten is poor in species, not only because of St. Maarten’s small size, but also because of habitat destruction, hunting, imported predators and hurricanes. One bird species, the Red-tailed Hawk, Buteo jamaicensis, and two kinds of reptiles, the Antillean Iguana Iguana delicatissima and the original population of the Green Iguana, Iguana iguana, have already been exterminated. Among the vertebrates, birds form the largest group. Especially the number of migrating birds and visitors is big. In total there are 39 resident and nesting birds on St. Maarten and 68 species of migrating birds and visitors have been observed. These include 19 sea birds, of which 10 species breed in or in the vicinity of the island. St. Maarten is classified as an important breeding area for seabirds. Several small rocky islands just off shore accommodate breeding colonies of seabirds. 2 Amphibians and reptiles are the next largest group of vertebrates. They are represented by 15 species. Bats are probably the only native mammals. There are six species on St. Maarten.

The subspecies of the tree lizard Anolis wattsi pogus can be regarded as an island-endemic species. The animal is extinct in other islands. Several vertebrates are endemic for the Lesser Antilles and the Virgin Islands, either at the species level or the subspecies level: one bat, one amphibian and six reptiles. The ground lizard Ameiva pleei, the tree lizard Anolis gingivinus, the gecko Sphaerodactylus sputator, the Grass-snake Alsophis rijersmai and the subspecies of the gecko Sphaerodactylus macrolepis parvus are limited to only a few islands. The White crowned Pigeon Columba leucocephala and the Red-Necked Pigeon Columba squamosa, both regionally and locally rare because of hunting, are still found in the island and could increase because of the diminished pressure of hunting. Among the breeding seabirds three, Audubon’s Shearwater Puffinus lherminieri lherminieri, the Brown Pelican Pelecanus occidentalis occcidentalis, and the Roseate Tern Sterna dougallii dougallii, are endangered and three, the Red-billed Tropicbird Phaeton aethereus mesonauta, the Sooty Tern Sterna fuscata fuscata, and the Least Tern Sterna albifrons antillarum, are possibly endangered. Of the invertebrates not much more is known than 170 names.

The main threats to the biodiversity of St. Maarten are habitat destruction and degradation caused by the growth of inhabited areas, tourism development and pollution. Since the fifties several people argued for the need to preserve valuable nature areas, not only for ecological motives, but also for the benefit of tourism. Stinapa-St. Maarten, the later St. Maarten National Heritage Foundation, and Stinapa Netherlands Antilles, have struggled continuously to establish a hilltop protected area and a nature/culture reserve Belvédère/Bishophill. Their aim should be supported. At present the necesary island legislation is being worked on. For effective nature management in St. Maarten complete floristic surveys are necessary, and further studies of the status of the island populations of regionally and locally scarce and/or endangered species. For now, a few conclusions can be drawn regarding the conservation of biodiversity on St. Maarten. For this conservation it is necessary to safeguard the largest possible contiguous areas of nature. To this aim the following areas are recommended for conservation and management: the ‘Hillsides’, Naked Boy Hill and surroundings, and the hills and coastal area between Guana Bay en Back Bay. For the benefit of the bats the top of Billy Folly is recommended, and for the avifauna the various ponds, coastal habitats and the little islands Pelican key, Molly Beday and Hen and Chickens.

A semi-detailed landscape-based vegetation map (scale: 1: 37,500) is presented for the 13 km2 Lesser Antillean steep volcanic island of Saba, Netherlands Caribbean. The map is based on a total of 49 vegetation plots that were sampled in 1999 using a stratified random sampling design and analysed using TWINSPAN cluster analysis. Three hundred and fourteen (314) plant species, representing 56% of the total known flora (565 species), were recorded in the sample plots. The principal lower sections of the island possess a tropical savannah climate whereas the upper slopes reaching a maximum altitude of 870 m can best be characterized as a tropical rainforest climate.
A total of two main and nine different sub-landscape types were distinguished based on geology, geomorphology and nine distinguished vegetation types. In Saba, sharp contrasts in soil, geomorphology and climatic factors are found on a small spatial scale and this meant that compared to the other islands of the Dutch Caribbean there is little mixing and merging of vegetation types at the landscape vegetation level. Consequently, vegetation type translates relatively directly into landscape vegetation units. Aside from important contrasts in vegetation that correspond to what is known about differences in soil and climate, our study also shows that large vegetation changes have taken place on the island since the survey by STOFFERS, five decades earlier. These largely appear to be due to three major forces: a) hurricane impacts; b) natural succession made possible due to diminished agricultural activity and; c) invasive plants and plant pest species.
The most recent hurricane, hurricane Georges, which struck the island one year before this study, clearly caused much damage to the vegetation, especially high on Mount Scenery. As a consequence, the elfin woodland vegetation has virtually disappeared, while remnant sections have been radically altered. Based on studies elsewhere in the region, the elfin woodland can be expected to take very long (if at all) to gradually recover. The impact of various hurricanes in the last 60 years has clearly caused major disturbance of the vegetation throwing it back into earlier stages of succession. The development of the “Tree fern brake” into “Pioneer forest” vegetation must be seen as a positive change where a secondary community had entered a higher stage in the sequence of succession. The virtual disappearance of the formerly prominent secondary shrub communities like Miconia thickets, Piper dilatatum thickets and Leucaena thickets can also be seen as likely evidence of natural successional forces thanks to diminished agriculture and woodcutting. Invasive species was the third major force of change that clearly appears to have been active on Saba in recent decades. The lasting impacts of insect invaders which have decimated formerly prominent Opuntia (cactus) and Tabebuia (tree) populations testify to the impact of invasive species as a major driver of recent vegetation changes on Saba.
Our field data show that most wilderness areas of Saba remain strongly affected by roaming grazing goats even though the contribution of goats to the local island economy is negligible. Goat dung or traces of grazing were recorded in or adjacent to 46% of the sample plots. Grazing by exotic mammals reduces the resilience of natural vegetation types and interferes with natural succession. Highest livestock densities and impacts seem to be in the more vulnerable coastal arid zones along the western and southern sections of the island with poor soil conditions and more open and shrubby vegetation. The development of ‘Dry evergreen woodland’ under similar conditions on the more remote, windy and salt spray-affected, but less-grazed, northern sectors of the island, suggest that those disturbed areas of the southern and western coastal zones should have potential for woodland recovery if and when goat grazing is reduced. Therefore, a key priority for terrestrial conservation in Saba should be to reduce feral grazer densities to allow vegetation recovery and reduce vulnerability to erosion. We suggest the use of pilot demonstration projects for grazer exclusion as a useful way to help build stronger arguments and public support for tackling the roaming goat problem in Saba.

Abstract:

Although the flora of Bonaire has been well studied three previously undocumented species have been found for Bonaire. Two of these three species are fern species and are new for the six islands of the Dutch Caribbean. The third species (Capparis linearis) occurs also on Curaçao and Aruba and is also a rare species on those islands. Data on the distribution of twelve rare species (eleven are previously unreported rare species for the Washington-Slagbaai National Park (WSNP) are also presented. A number of publications indicate the deleterious effects of introduced goats, donkeys and pigs on the vegetation and flora of islands. These animals are also found in the WSNP. The lack of saplings and the (very) small numbers of seedlings of only a few rare tree species found in the present study are ascribed to the deleterious effects of goats, donkeys and pigs. 

Abstract:

Saba is the smallest of the three Windward Islands in the Netherlands Antilles, with an area of 13 km2. Saba is the northernmost island within the Lesser Antilles' inner curve. The island is actually the top of a dormant volcano. Typical of the island are the steep cliffs, deep ravines running radially and sheer cliff coasts. The highest top is the Mt. Scenery, commonly called “The Mountain”. About 1200 people live on Saba in four villages all situated on the south- eastern half of the island. The northwestern half is not inhabited. Only a small part of the land area is used for agriculture or cattle breeding. In the south there is a stone crusher facility.

The climate is tropical and according to the system of Köppen it falls between a savanna- and monsoon climate, however the big differences in altitude cause a large variety of climatologi- cal conditions. Above 450 meters the rainfall and humidity gradually increase until they reach their maximum on the top of The Mountain. The top of The Mountain is nearly always veiled in clouds. The diversity of plants and plant-communities is caused by these variations in climatological conditions.

With 520 species the small island of Saba possesses practically the same number of species of wild plants as the much larger island of St. Maarten. The number of ferns is especially large. Saba has no island-endemic species among the plants. However, the geographical distribution of six species and one variety is limited to only a few islands, and 4.6% of the species is en- demic to the Lesser Antilles and the Virgin Islands. The Bryophyte flora consists of 48 leaf mosses and 31 liverwort species.

Expressing the differences in climatological conditions as the altitude increases, a series of plant communities are found, ranging from Croton thickets to (secondary) rainforest and elfin woodland. The elfin woodland is of a regionally rare type. The palm brakes and the ravine rainforest are practically undisturbed by human activities. They belong to the few virgin vegetations of the Netherlands Antilles. The tree-fern brakes are a special type of secondary vegetation, which develops under conditions of high humidity. The secondary rainforest zone was seriously disturbed in the past. There are still small cultivation plots here. Wherever the vegetation is left alone however, new rainforest is developing. The rainforest is one of the most species-rich plant communities. This is also where the greatest number of leaf mosses are found on Saba. The evergreen and seasonal formation zones were also disturbed in the past, however the vegetation is recovering. The great variety of forest formations on The Mountain makes this area highly attractive to visitors. The uninhabited area in the northwest of the island is important to the survival of various small island populations and has a high scenic value.

Saba's fauna has very few species compared to a similar area on the mainland, but this is to be expected from a relatively isolated small island.
Among the vertebrates the birds form the largest group, represented by 26 local and breeding species. In addition 36 migrating species are present every year on a temporary basis. Amphibians and reptiles are the next largest group of vertebrates with eleven species.

Bats are the only mammals on Saba that were not introduced by humans. This group is represented by five species. There is one island endemic among the vertebrates: the lizard Anolis sabanus. One species, the Red-bellied Racer Alsophis rufiventris is limited to Saba and St. Eustatius and is listed on the “Red List of Threatened Animals” of the IUCN. Various vertebrates are endemic to the Lesser Antilles and the Virgin Islands, either at the species level or the subspecies level: two bats, nine birds, one amphibian and one reptile. The gecko Sphaerodactylus sabanus, the bat sub-species Natalus stramineus stramineus and the Trembler Cinclocerthia ruficauda pavida have a geographical range, which is limited to only a few islands. Among the birds and reptiles there are species of which the population has declined because of hunting or the gathering of the eggs, like for instance the Rednecked Pigeon Columba squamosa, the Audubon's Shearwater Puffinus lherminieri, and the green Iguana Iguana iguana. A few bird species are regionally almost completely limited to the habitat of the rainforest and the mountain formations, e.g. the Purple-throated Carib Eulampis jugularis, the Trembler Cinclocerthia ruficauda pavida and the Blue-crowned Euphonia Euphonia musica flavifrons, which has not been seen since 1952. The possibly endangered Bridled Quail-dove Geotrygon mystacea and Red-billed Tropicbird Phaeton aetherius mesonauta breed on Saba. Of the latter the breeding population on Saba is the largest of the Caribbean region. Of the invertebrates not much more is known than 86 names. The Mountain Crab Gecarcinus ruricola is endangered through hunting.

In the past the nature of Saba was mainly impacted by activities related to agriculture and cattle breeding. Today, the most important threats are destruction and degradation of habitat by development in general, especially because of the lack of regulations.
Since the nineteenfifties there is a lot of interest in the conservation of nature and the beautiful scenery. The necessity to preserve the top of The Mountain is mentioned many times, accompanied by specific plans. A group of people even promoted the idea to declare the whole island of Saba a conservation park. Up until today however, the terrestrial nature on the island remains unprotected.

Several studies have produced a wealth of data, yet not enough for optimum nature conservation. Further vegetation research of the top of The Mountain and the northern part of the island is necessary, as well as further study of the status of the island populations of regionally rare and/or endangered species. Also additional knowledge of the invertebrates is needed.

For now a few general conclusions can be drawn with respect to conservation of the biodiversity. For this conservation it is necessary to secure large contiguous areas. For small islands this can be problematic, but there are still a lot of possibilities on Saba. In particular the uninhabited northwestern part of the island and The Mountain above 450 meters would qualify. Specific conservation is required for the breeding places of the Audubon's Shearwater, Tropicbirds and other seabirds on Green Island and Diamond Rock. 

In view of their ecological importance and the abundance of threats on a developing Caribbean island, we surveyed the bats of Curaçao, Netherlands Antilles, and examined changes in the populations of seven threatened species over a decade, using previously published data as a baseline for comparison. The most important caves for bats (in terms of species representation and reproduction) were visited yearly, and monthly in 2001. Noctilio leporinus still occurs on the island, but does not appear to be numerous (six observed in 2003). We captured Myotis nesopolus nesopolus, but its roosting sites remain unknown. Leptonycteris curasoae curasoae numbers varied greatly, even within a year, and it may travel to and from other islands and Venezuela. Overall, however, the population of this species on Curaçao seems to be declining (1000 in 1993 and 625 in 2003); the disappearance of this pollinator could have severe consequences for the Curaçao ecosystem. Mormoops megalophylla intermedia is declining as well; in 2003, we counted 403 individuals including 75 pups, from 500 to 600 adults in the 10 previous years, representing a 25–30% decline in 1 year. We estimated the population of Natalus tumidirostris to be 890 in 2003. We also found a group of 60 Pteronotus davyi in Kueba di Ratón in 2003.Glossophaga longirostris elongata (1417 individuals counted) is the only species for which our data indicate relative stability over 10 years; L. curasoae and Mor. megalophylla are declining and other species must be monitored closely. Most caves are disturbed; four major caves require attention for the conservation of the most fragile species. Without immediate attention, Mor. megalophylla, in particular, risks imminent extinction. Despite problems associated with bat counts on Curacao, it is clear that regular surveys are crucial to understand bat populations and their fluctuations in caves, and to allow management responses to declines, particularly for areas undergoing rapid urbanization. 

Abstract:

A semi-detailed landscape-based vegetation map (scale: 1: 37,500) based on field data from 1999 has been available as an update of Stoffers’ 1956 map of the Lesser Antillean island of St. Eustatius, Netherlands Caribbean, but up to now was never finalized or published. In this report we complete the documentation of that map to provide new insights into vegetation change over a period of more than 40 years, and a quantitative reference point for future studies on landscape-level vegetation development for the island.

The principal lower sections of the 21 km2 island of St. Eustatius possess a tropical savannah climate according to the Köppen (1931) classification system, and the documented flora of the island amounts to 505 species. Color aerial photographs (1: 8,000) taken in 1991 and field data from 1999 were used to produce the map. A total of 84 vegetation sample plots were analysed using a stratified random sampling design and TWINSPAN cluster analysis.

Four main and 16 sub-landscape types were distinguished based on geology, geomorphology and different mixes and expressions of the component vegetation types. The five principal landscape types are in descending order of importance: H1, H2, M4, M9 and C, and covered some 67 % of the seminatural habitat of the island. H1 and H2 are the Pisonia-Justicia hills and Pisonia-Bothriochloa hills and are limited to The Mountains area. Analysis of the sampling data resulted in the distinction of 13 (semi)natural vegetation types. The three principal vegetation types were, the Pisonia-Justicia type, Pisonia-Ayenia type and Bothriochloa-Bouteloua type which together accounted for 38 % of total (semi)natural vegetation cover. The following well-developed vegetation types of St. Eustatius represent primary climax communities: Types 1, 2, 3, 5 and 7, all found in and around the Quill in the southwestern part of the island. A comparison of the vegetation types in the present study with those of Stoffers (1956) showed that only one vegetation type closely resembles one in Stoffers’ study. Major changes have taken place in certain types of the natural vegetation of the island in the intervening five decades.

The majority of the central sections of the island around Oranjestad the so-named “Cultuurvlakte”, amounting to approximately 25 % of the surface of the island, have suffered intensive disturbance due to past agriculture, livestock husbandry and invasive species and were not mapped. Only a small remnant portion of the semi-natural lowlands vegetation (L1 and L2) was left in the coastal reaches of Billy’s Gut. Nevertheless, this area is heavily affected by grazing and the invasive vine Antigonon leptopus.

A comparison with the 1950s vegetation map by Stoffers shows that the rarest and most valuable elfin woodland vegetation of the rim of the Quill crater had been largely lost and that the areas he described as “Montane thickets” (Type 2) had declined and been degraded. We speculate that these losses may be most directly attributable to the impact of recent hurricanes and/or grazing by introduced livestock. On the lower slopes of the Quill, several areas mapped by Stoffers as farmland had been abandoned and have evidently regenerated into mixed deciduous and evergreen thorny woodlands.

The vegetation of the Mountains area showed some recovery since the 1950s. There were more evergreen bushes, and less Acacia and Leucaena than Stoffers described. The vegetation Stoffers described for the lowlands had more Acacia than we found but the invasive Antigonon has since dramatically increased as a ubiquitous and often dominant species. The former importance of Opuntia prickly pear cacti in disturbed vegetations has dramatically declined since the 1950s. We ascribe this to the likely effect of the invasive parasitic insect Cactoblastis cactorum. In the 1980s and 1990s many Opuntia cacti were seen affected by this insect (G. Lopes, pers. comm.).

Our field data show that all wilderness areas of St. Eustatius remained heavily affected by grazers. This reduces the resilience of natural vegetations and interferes with natural succession by imparting heavy losses to hardwood seedlings and saplings (see e.g. Melendez-Ackerman et al. 2008), by reducing plant biomass (which increases exposure to wind and sun), and by favoring hardy invasive plant species. In Curaçao, large scale reduction in densities of feral grazers in the Christoffelpark since 1993 has led to rapid recovery of several rare plant species and vegetation types. The problem of feral livestock remains severe. Therefore the number one priority for terrestrial conservation in St. Eustatius will be to reduce feral grazer densities and impacts in key wilderness areas.

Management Recommendations:

Parts of the natural areas of both The Mountains and the Quill are protected by law, but goats and other roaming livestock are omnipresent in all habitats and continue to have evident impacts on the vegetation. Aside from generally reducing the resilience of the vegetation to major disturbance, intensive impact in the herbaceous layers likely affects regeneration of rare hardwood species directly through selective predation and indirectly by overall desiccation and increased exposure to the elements. Goats have a broad diet in the region and species eaten include canopy, mid-canopy and understory species (Melendez-Ackerman et al. 2008). Vegetation degradation further also affects the competitive balance towards (unpalatable) invasive species such as Antigonon leptopus, Pedilanthus tithymaloides, and Leucaena leucocephala, which have expanded massively into natural habitat in the last 50 years. Not only is general vegetation degradation suggested as a problem to endangered breeding seabirds, but goats likely also directly trample nesting burrows of seabirds (Collier & Brown 2009).

Consequently, priorities for nature conservation are to:

• Reduce grazer densities in all areas,
• Protect the most sensitive vegetations using total grazer exclusion, and
• Experiment with methods to spur vegetation recovery, including erosion control, propagation of rare and endangered species and reforestation with indigenous species
• Establish permanent plots in areas with the most sensitive vegetations in order to better understand causal factors of short- and longer term changes. 

This report is part of the Wageningen University BO research program (BO-11-011.05-004) and has been financed by the Ministry of Economic Affairs, Agriculture and Innovation (EL&I) under project number 4308202004.