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We assessed the damage caused by selection logging of mahogany in a tropical forest in northern Belize and compared it with damage reported in other Neotropical logging and disturbance studies. We mapped skid roads and tree felling sites, and assessed soil compaction, loss of canopy cover, damage to saplings and trees, seedling survival and seedling height growth. Logging had been conducted using hand crews with chain saws and cable skidders. Logging directly affected 11.9 ha (12.9%) of the 92.3 ha logging area. Canopy cover decreased the most at logging gaps, and soils were most compacted on skid roads. Soil compaction was much greater on roads where more than one tree had been skidded. For the whole logged area, canopy cover declined 2% and compacted soils covered 3.8% of the area. Seedling height growth was unaffected by soil compaction, but seedling survival was less on compactedsites. About 50% of the trees and about 15% of the saplings were damaged in gaps and along skid roads. However, only 4.8% of the trees and 1.9% of the saplings were damaged for the logged area as a whole. The most common kinds of damage included scraped bark, snapped tops, and run-over stems. Although this logging operation had relatively lowimpacts compared with other logging operations in the Neotropics, itmay not be silviculturally sustainable because its disturbance may be insufficient to promote adequate mahogany regeneration. [ABSTRACT FROM AUTHOR]

We identified and.measured the DBH of all trees >/= 10 cm DBH in two10 x 500 m plots in the Quebrada de Oro Valley, in Bladen Nature Reserve, southern Belize, Central America. The study area was at 150 m elevation on limestone soils and receives 2500 to 3000 mm of rainfall year-1. In the two plots combined there were 359 trees with >/= 10 cm DBH, of which 22 (6.1%) were with >/= 70 cm DBH. Basal area was 32.81 m2. There were 73+ species. Eight species accounted for 50%, of the stems. Thirty-six of the 73+ species were represented by only one stem. Astrocaryum mexicanum, a palm with < 10 cm DBH, dominated the understory. This forest stand is unusual in the neotropics for its low density of stems with >/= 10 cm DBH, large number of big trees, and high proportion of species represented by only one stem. It is among the most structurally impressive and species-richforests in Belize. We suggest that favorable soil conditions, shielding by surrounding hills from hurricane winds, and immigration of species from a variety of nearby but different forest types explain thisforest's exceptional structure and high species richness. [ABSTRACT FROM AUTHOR]

The rapid disruption of tropical forests probably imperils global biodiversity more than any other contemporary phenomenon. With deforestation advancing quickly, protected areas are increasingly becoming final refuges for threatened species and natural ecosystem processes. However, many protected areas in the tropics are themselves vulnerable to human encroachment and other environmental stresses. As pressures mount, it is vital to know whether existing reserves can sustain their biodiversity. A critical constraint in addressing this question has been that data describing a broad array of biodiversity groups have been unavailable for a sufficiently large and representative sample of reserves. Here we present a uniquely comprehensive data set on changes over the past 20 to 30 years in 31 functional groups of species and 21 potential drivers of environmental change, for 60 protected areas stratified across the world’s major tropical regions. Our analysis reveals great variation in reserve ‘health’: about half of all reserves have been effective or performed passably, but the rest are experiencing an erosion of biodiversity that is often alarmingly widespread taxonomically and functionally. Habitat disruption, hunting and forest-product exploitation were the strongest predictors of declining reserve health. Crucially, environmental changes immediately outside reserves seemed nearly as important as those inside in determining their ecological fate, with changes inside reserves strongly mirroring those occurring around them. These findings suggest that tropical protected areas are often intimately linked ecologically to their surrounding habitats, and that a failure to stem broad-scale loss and degradation of such habitats could sharply increase the likelihood of serious biodiversity declines.

Researchers recognize that society needs accurate and comprehensive estimates of the economic value of rain forests to assess conservation and management options. Valuation of forests can help us to decide whether to implement policies that reconcile the value different groups attach to forests. Here we have measured the value of the rain forest to local populations by monitoring the foods, construction and craft materials, and medicines consumed or sold from the forest by 32 Indian households in two villages in Honduras over 2.5 years. We have directly measured the detailed, comprehensive consumption patterns of rain forest products by an indigenous population and the value of that consumption in local markets. The combined value of consumption and sale of forest goods ranged from US$17.79 to US$23.72 per hectare per year, at the lower end of previous estimates (between US$49 and US$1,089 (mean US$347) per hectare per year). Although outsiders value the rain forest for its high-use and non-use values, local people receive a small share of the total value. Unless rural people are paid for the non-local values of rain forests, they may be easily persuaded to deforest.

Studies that are unprecedented in scale, detail or approach show that niche partitioning contributes less, and chance events more, than expected to maintaining tree species richness via gap dynamics in tropical and temperate forests. Some tree species are differentially adapted for regeneration in different gap microenvironments. However, the stochastic availability of gaps, and limited recruitment of juveniles, mean that gaps are filled mostly by chance occupants rather than by best adapted species. This chance survival can slow competitive exclusion and maintain tree diversity. Gap dynamics do not explain the latitudinal gradient in tree richness.

Earthquakes occasionally denude large areas of tropical forest: for example, 54 square kilometers in Panama in 1976 and 130 square kilometers in New Guinea in 1935. Earthquake rates in New Guinea, but not in Panama, are sufficiently high so that substantial areas of disturbed, nonclimax forest may accumulate. In New Guinea, earthquake-caused landslides are as important as tree falls in the disturbance regime.