An extraordinary place
The Guiana Shield of northern South America is a vast geological formation dating back to Precambrian times. It underlies Guyana, Surinam, French Guiana as well as parts of Brazil, Venezuela and Columbia. The vegetation that clothes this ancient landscape is the most intact rainforest in the world and it harbours a huge abundance and diversity of animals and plants. This area comprises the largest expanse of undisturbed tropical moist forest anywhere, and it's the least studied of the world's great rainforests. Many of the animal and plants groups have high levels of endemism (species that occur here and nowhere else). The proportion of endemic plant species and genera across the Guiana Shield is estimated to be in the region of 40%.
Guyana is a little smaller than the UK but only has a human population of 800,000, most of whom live in the capital, Georgetown, and along the coastal strip. Because of the very low population pressure, the country's natural vegetation remains largely intact with about 80% of the land area covered in dense forest. The biodiversity of Guyana is known to be very high with 8,000 species of plants (including 1,000 tree species) of which about half are endemic and more than 2,700 vertebrate species.
What we hoped to achieve
The BBC team's primary job was to film and carry out a rapid biological assessment, primarily at the Upper Essequibo Conservation Concession, which is managed by Conservation International Guyana. After a stay at base camp, deep in the rainforest, the team broke into smaller groups to investigate and film animals on the vast savannas of South Rupununi, the region around Kaieteur Falls and the upper reaches of the Rewa River to the west.
Charles Darwin described the rainforests of the neotropics as, 'one great wild untidy luxuriant hothouse made by nature for herself', and standing at base camp in the Upper Essequibo Conservation Concession, you know exactly what he meant. In all directions, mile upon mile of forest echoes with the shrill noise of insects, the calls of birds including the aptly-named screaming piha and, in the distance, the loud, territorial whoops of howler monkeys. On the shaded forest floor, bright-eyed spiders and beetles leap and scuttle among the leaf litter and every now and then columns of army ants, scouring the ground for anything they can kill and eat, flush out all kinds of wildlife from their hiding places. These raids are followed by numbers of small birds, which pick off the fleeing invertebrates.
Guyana might well be called the land of giants for there are many creatures much larger than related species found elsewhere. Guyanese rainforests are home to the giant otter, the world's largest mustelid; the capybara, a dog-sized rodent; the anaconda, the world's heaviest snake and the harpy eagle; the largest eagle in the world and one that specialises in plucking sloths and monkeys from the tree tops. There is even a giant arachnid - the Goliath spider with fangs 2.5cm long and minutely-barbed, abdominal hairs which it flicks into the face of potential predators to great effect. All of these charismatic species and many more were seen and filmed during the course of the expedition.
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Stretching nearly 1,000km, the Essequibo River is the longest river in Guyana. It rises in the Acarai Highlands near the Brazilian border and flows north to the Atlantic Ocean. Its many tributaries give rise to smaller and smaller streams and creeks. This rich mosaic of freshwater habitats was the hunting ground for team member Phil Willink, a fish biologist from the Chicago Field Museum. During the expedition he collected more than 1,000 specimens representing 9 orders, 29 families, 79 genera and approximately 100 species of fish of which 10% are potentially undescribed species.
The expedition captured on film the moment of discovery of the two strongest candidates for fish species new to science, a small banded fish (Hemiodus sp.) netted near the base camp and a parasitic catfish (Vandellia sp.) that fell out of the gills of a larger catfish species. These slender, transparent, eel-like fish known locally as candiru, enter the gill openings of fish to suck the host's blood.
The richness of fish species more than equals that of other little-known areas in the neotropical realm. Phil reckons that another survey conducted at a time when river levels were lower would undoubtedly yield two to three times as many species and that there are almost certainly more than 200 species in the immediate region. Many of them may be endemic to the Essequibo basin.
Phil also found that the smaller streams didn't have as many species as the larger rivers but these were particularly rich in terms of aquarium species, with many beautiful tetras, catfishes, and cichlids. 'You could fill every pet store in the UK with what we found' he was heard to remark.
Almost nothing is known about the seasonal movements, life histories and juvenile recruitment of the food fish species in the larger rivers but the large number of big piranhas is a good sign that there is little human impact in the areas studied. Large top-level predators such as piranhas and sabre-toothed characin are the first to be lost to humans either as food or fishing trophies.
Phil Willink considers the aquatic ecosystem of the Upper Essequibo Conservation Concession to be one of the most pristine, if not the most pristine, on the planet and thinks the only other comparable places are in the far Arctic, Antarctic and possibly other pockets on the Guiana Shield.
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Reptiles and amphibians
During a stay of only eight days at base camp, Amy Lathrop, a herpetologist from the Royal Ontario Museum conducted surveys day and night by walking transects established around the camp, investigating the smaller waterways, drifting by boat up creeks and along the banks of the Essequibo River as well as sifting through leaf litter. She recorded 15 amphibian species, 15 reptiles (6 snake species, 8 lizard species and one turtle species). There were healthy populations of crocodilians in the area; the spectacled caiman (Caiman crocodiles), the black caiman (Melanosuchus niger), which has been under severe pressure in Brazil and possibly two species of dwarf caiman, Cuvier's dwarf caiman (Paleosuchus palpebrosus) and Schneider's dwarf caiman (Paleosuchus trigonatus).
The most common amphibian was the gladiator frog (Hyla boans) and several species of ditch frog (Leptodactlyus spp.). The most common reptiles from undisturbed habitat, though not abundant, were diving lizards (Uranoscodon superciliosus) and Amazon tree boas (Corallus hortulatus) along the Essequibo River. Other snakes recorded were the emerald tree boa (Corallus caninus) that feeds on rodents and bats, the false coral snake (Erythrolamprus aesculapii) a snake-eating species, the parrot snake (Leptophis ahaetulla) that feeds on frogs, lizards and small birds, the blind snake (Typhlops reticulatus), a nocturnal insect-feeding species and the snail-eating snake (Dipsas variegata) that feeds exclusively on tree snails and slugs.
In the predominantly greenheart forest near to the base camp three species were found that were not seen elsewhere; the turnip-tailed gecko (Thecodactylus rapicauda), the monkey frog (Phyllomedusa bicolor) and Peter's jungle frog (Leptodactylus petersi). It is important to point out that herpetological surveys carried during the early part of the rainy season and over a wider area would have yielded even more species but given the rich variety of habitat types present in the concession there is certain to be very rich fauna of reptiles and amphibians.
One of the herpetological highlights was a species of shield frog (Adelophryne sp.), which does not match the description of any of the five known species in the genus.
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Burton Lim of the Royal Ontario Museum sampled small mammals, including bats, using live traps and mist nets. In an eight-day period, 19 species of bats, 4 species of rodents, and 1 species of opossum were documented along the length of one forest trail cut near the base camp. The bats present include the vampire bat and the frog eating bat as well as insect-eating, fruit-eating and nectar-feeding species. Several of the bat species collected carried ectoparasitic flies belonging to the families Streblidae and Nycteribiidae, some of which resembled minute, wingless crickets. It is more than likely that two of these bat flies will be species new to science.
In previous studies at Iwokrama Forest, a reserve to the north, a team of four specialists working for 12 weeks recorded 100 species of small mammals. In a tenth of the time, Burton recorded 24 species indicating that the Upper Essequibo Conservation Concession may have an equally high biodiversity.
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While nobody on the team had the specific job of recording birds, dozens of species were seen including several species of kingfisher, heron and humming bird.
Raptors included osprey, swallow-tailed kite, fish eagle and black, turkey and yellow-headed vultures. Almost every day the strident calls of vividly coloured macaws were heard over the forest and the normally shy black curassow could be seen foraging on the forest floor under fruiting trees.
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For all the vertebrate groups studied during the trip, the species accumulation curve (the total number of species recorded) continued to rise steeply and even during the last few hours of sampling, previously unrecorded species were being added to the list. This demonstrates that even for large species, we had not seen everything during our stay. While it might be possible in time to tally all the fish, reptiles or bird species of the area, to quantify the forest and freshwater invertebrates would be a truly Herculean labour lasting decades and requiring teams of zoologists working from the top of the canopy down to soil and river sediment. The small amount of trapping and hand collecting carried out, yielded thousand of specimens of insects and spiders representing several hundred species. It is hard to say what percentage of these species will turn out to be new to science but in an area where so many new vertebrate species can be found in such a short time, it is likely to be 20% or more.
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A wildlife hotspot
Invertebrates are near the bottom of many terrestrial and aquatic food chains. Without great quantities of invertebrates, larger species would not be able to survive. The large number of vertebrate species present, including all of the primate species recorded in Guyana, as well as jaguar, caiman and harpy eagle (top-level predators) show clearly that the Upper Essequibo Conservation Concession is a uniquely pristine area. Taking into account the short duration of our assessment, the biodiversity recorded was astounding and likely to be as high as anywhere on Earth. Not only unspoiled, but also largely undisturbed; there were none of the familiar signs associated with hunting or fishing and many of the animals encountered showed little fear of humans.
There is archaeological evidence of some human presence here in what is believed to be pre-Columbian times but no records from recent times. In the living memory of villagers from this area the only humans that have ventured far into the interior of this region have been balatá tappers who collected and dried the milky sap of manilkara trees to make a hard, water resistant, rubber-like material.
This biodiversity hotspot is without doubt one of the least explored rainforests on the planet but it is poised on the brink of changes that could have devastating effects on its rich flora and fauna. Logging and mineral extraction could wreak havoc in habitats that have survived undisturbed for many thousand of years. The damage would not just affect terrestrial species through habitat loss and fragmentation but also affect the river communities, especially the benthic (bottom-dwelling) fish species. Because they forage and spawn on the bottoms of rivers and streams, they are susceptible to sediment covering their preferred habitat. Excessive erosion, such as caused by deforestation, would severely impact upon these species. Even logging outside the Upper Essequibo Conservation Concession would have an effect because many of the larger streams have their headwaters outside the boundaries of the Concession, and sediment could be carried downstream all the way to the Essequibo River.
The lack of baseline information for the area and its unspoiled nature makes the Upper Essequibo Conservation Concession in particular and the region in general, a high priority for immediate conservation action.
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