Pors, L.P.J.J.

We estimated the population sizes of the three species of columnar cacti that grow on the island of Curaçao using ground and aerial transects, and we examined the island’s carrying capacity for two species of nectar-feeding bats that depend on nectar from the flowers of these cacti. We calculated carrying capacity based on the daily availability of mature flowers between January and December 1993 and the field energy requirements of bats as estimated from an equation for eutherian mammals (low estimate) and one for passerine birds (high estimate) based on body mass. Additional energy requirements of pregnancy and lactation were taken into account. We estimated that 461,172 columnar cacti were present on Curaçao (38% Subpilocereus repandus, 51% Stenocereus griseus, and 11% Pilosocereus lanuginosus). May through September are the critical months when bats rely most heavily on cactus for food. July 1993 was a bottleneck with the smallest number of mature flowers per day. July and August were months of greatest energy demand because females were lactating. We estimate that the carrying capacity for Glossophaga longirostris in July, when the bat (Leptonycteris curasoae) population was 900, was near 1200, an estimate that fits the observed population size of nectar-feeding bats on the island. We suggest that the extensive removal of native vegetation occurring on Curaçao be strictly regulated because further destruction of the cacti will result in a decrease and potential loss of the already low populations of nectar-feeding bats.

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. 

Caribbean corals have suffered from bleaching, diseases and Diadema die-off. Reefs on narrow shelves adjacent to high human population and many fishers (Colombia, CuraGao, Jamaica, Venezuela) suffer from imcreased terrestrial run- off and over-fishing, showing signs of degradation (fewer fish, more algae, less coral cover). Where shelves or banks are wide or far from human populations, reefs are less dis- turbed. Islands with fewer people and little fishing (Bonaire, Cayman) have good reef resources. Here, diving tourism is important, and there is more awareness of the need for reef conservation. Cayman has the best developed national coastal area management plan. Most of the other countries have Marine Protected Areas. These stimulate improved Coastal Area Management, aided by increasing numbers of Non-Governmental Organizations (NGOs). 

The purpose of this survey was to describe and map the natural and cultural resources of the marine environment with a view to sustainable development of these resources for tourism.The following main habitat types were identified: coral-encrusted rock, true coral reefs, sand with algal beds, and artificial habitat (wreck sites). The most important areas for recreational use and further tourism development are the reef complex south of the city pier, the reefs of Jenkins Bay and the archaeological sites in Oranjebaai.
In addition to describing and mapping the resources, an inventory of uses of the marine environment was made, being fisheries, diving and snorkeling, anchoring and ship's traffic. Individual uses were mapped and these maps were overlayed to show areas of conflict between uses. The overlays formed the basis for a zoning plan for the marine environment. This plan identifies certain zones for different uses, so as to avoid conflicts between users. The zoning plan proposes two marine park
zones, two archaeological zones, a large anchorage/harbor zone, traffic zones and a fisheries management zone. Since the institutional structure for managing the marine environment and enforcing the regulations of the zoning plan is not available at present, creation of a new non-governmental body is recommended for management. All interest groups should be represented in such a body. Once the Island Government approves the recommendations and the proposed zoning plan, a detailed
project proposal and budget need to be drafted and submitted for funding.