by deepgreenresistance | Dec 1, 2011 | Biodiversity & Habitat Destruction
By Mongabay
Global forest cover, as well as forest loss, is lower than previously estimated by the Food and Agriculture Organization (FAO), according to a new satellite-based assessment that replaces the self-reporting system previously used by the U.N. agency.
The survey found the world’s total forest cover amounted to 3.69 billion hectares, or roughly 30 percent of global land area, in 2005. FAO’s Global Forest Resources Assessment 2010 (FRA 2010) — which was based on the old system — put total forest cover at 4.06 billion hectares.
FAO says that nearly half (44 percent) the world’s remaining forest cover lies in the tropics, while another third is in boreal regions. Temperate forests account for 13 percent of the global total, while sub-tropical forests amount to only 9 percent.
The remote sensing survey also evaluated change in forest cover. It found a net reduction in global forest area between 1990 and 2005 of 72.9 million hectares, or roughly a third lower than the previous estimate of 107.4 million hectares. Much of the discrepancy came from better analysis of African forests, where self-reported data was out of date.
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Distribution of global forest area (2005) by climatic domain. Courtesy of FAO. |
The satellite-based survey showed a jump in deforestation between 2000 and 2005 relative to the 1990s. The rate of net forest loss increased 56 percent from 4.1 million hectares per year in the 1990s to 6.4 million hectares per year from 2000-2005. In contrast, the previous assessment reported a decrease in deforestation between the two periods. Overall the vast majority of forest loss occurred in the tropics where forests declined by an average of 6.9 million hectares per year during the period (6.3 million ha in the 1990s, 8 million ha from 2000-2005). Other regions — the boreal, temperate, and subtopics — experienced increases in net forest cover due to reforestation, natural forest recovery, and establishment of plantations.
Excluding forest recovery, reforestation, and plantations, the global deforestation rate averaged 14.5 million hectares per year over the entire assessment period, roughly equivalent to prior estimates. Tropical deforestation increased from roughly 8.2 million hectares per year in the 1990s to about 10 million from 2000 to 2005.
FAO says its assessment does not adequately account for changes in tree cover in areas where the canopy is less than 30 percent. Forests will low canopy cover are usually degraded or occur in dry areas.
FAO did not release data for individual countries. That assessment will be available at a later date.
by revolutionofthelilies | Oct 23, 2011 | Biodiversity & Habitat Destruction, Climate Change
The biodiversity loss caused by climate change will result from a combination of rising temperatures and predation — and may be more severe than currently predicted, according to a study by University of British Columbia zoologist Christopher Harley.
The study, published in the current issue of the journal Science, examined the response of rocky shore barnacles and mussels to the combined effects of warming and predation by sea stars.
Harley surveyed the upper and lower temperature limits of barnacles and mussels from the cool west coast of Vancouver Island to the warm shores of the San Juan Islands, where water temperature rose from the relatively cool of the1950s to the much warmer years of 2009 and 2010.
“Rocky intertidal communities are ideal test-beds for studying the effects of climatic warming,” says Christopher Harley, an associate professor of zoology at UBC and author of the study. “Many intertidal organisms, like mussels, already live very close to their thermal tolerance limits, so the impacts can be easily studied.”
At cooler sites, mussels and rocky shore barnacles were able to live high on the shore, well beyond the range of their predators. However, as temperatures rose, barnacles and mussels were forced to live at lower shore levels, placing them at the same level as predatory sea stars.
Daily high temperatures during the summer months have increased by almost 3.5 degrees Celsius in the last 60 years, causing the upper limits of barnacle and mussels habitats to retreat by 50 centimeters down the shore. However, the effects of predators, and therefore the position of the lower limit, have remained constant.
“That loss represents 51 per cent of the mussel bed. Some mussels have even gone extinct locally at three of the sites I surveyed,” says Harley.
Meanwhile, when pressure from sea star predation was reduced using exclusion cages, the prey species were able to occupy hotter sites where they don’t normally occur, and species richness at the sites more than doubled.
“A mussel bed is kind of like an apartment complex — it provides critical habitat for a lot of little plants and animals,” says Harley. “The mussels make the habitat cooler and wetter, providing an environment for crabs and other small crustaceans, snails, worms and seaweed.”
These findings provide a comprehensive look at the effects of warming and predation, while many previous studies on how species ranges will change due to warming assume that species will simply shift to stay in their current temperature range.
Harley says the findings show that the combined effects of warming and predation could lead to more widespread extinction than are currently predicted, as animals or plants are unable to shift their habitat ranges.
“Warming is not just having direct effects on individual species,” says Harley. “This study shows that climate change can also alter interactions between species, and produce unexpected changes in where species can live, their community structure, and their diversity.”
From ScienceDaily: http://www.sciencedaily.com/releases/2011/11/111128115645.htm
