400-year study finds Northeast forests resilient, changing

Sep. 5, 2013 — A joint Harvard-Smithsonian study released today in the journal PLOS ONE reveals how much — and how little — Northeastern forests have changed after centuries of intensive land use.A hike through today’s woods will reveal the same types of trees that a colonial settler would have encountered 400 years ago. But the similarities end there. Jonathan Thompson, research associate at the Smithsonian Conservation Biology Institute and lead author of the new study, explains, “If you only looked at a tree species list, you’d have the impression that Northeast forests haven’t changed. But once you start mapping the trees, and counting them up, a different picture emerges.” Thompson adds, “In some ways the forest is completely transformed.”To draw these conclusions, Thompson and his colleagues compared colonial-era tree records to modern US Forest Service data across a 9-state area stretching from Pennsylvania to Maine.Their results show stark contrasts between pre-colonial forests and today. Maples have exploded across the Northeast, their numbers increasing by more than 20 percent in most towns. Other tree types have declined sharply. Beeches, oaks, and chestnuts show the most pronounced loss — big trouble, Thompson notes, for wildlife that depend on tree nuts for winter survival.Pine numbers have shifted more than any other tree type, increasing in some places, decreasing elsewhere. Thompson pins this variability to ecology and economy: “Pine is valuable for timber, but quick to return after cutting. It has a social and environmental dynamism to it.”The nine states in the study share a similar — and notable — forest history: during the 18th and 19th centuries, more than half the forestland was cleared for agriculture and cut for timber. …

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Typhoid’s lethal secret revealed

July 10, 2013 — Typhoid fever is one of the oldest documented diseases known to have afflicted humankind but what makes it so lethal has remained a mystery for centuries. In a study appearing online July 10 in the journal Nature, Yale researchers offer an explanation of how the devastating disease marked by delirium and stupor still kills 200,000 people every year — and also suggests the basis of a future vaccine.The culprit appears to be a powerful toxin possessed by Salmonella typhi, the bacterium that causes typhoid fever. Yale scientists for the first time describe the structure of the typhoid toxin and show that it causes disease in mice. The toxin helps explain why typhoid fever has such different symptoms than an infection by its close genetic cousin Salmonella, the common cause of food poisoning.”What makes this so exciting for us is that vaccines and therapeutics that target toxins have an excellent track record of success,” said Jorge Galan, the Lucille P. Markey Professor of Microbial Pathogenesis and senior author of the paper.Typhoid fever is believed to have killed Athenian leader Pericles and a third of the population of the Greek city in 430 B.C. during the Peloponnesian War and has perplexed doctors ever since. Untreated, it kills up to 20 percent of those it infects, however many of those who survive remain carriers for life but show no symptoms. This fact explains why fever, illness and death followed from job to job the notorious carrier Mary Mallon, best known as Typhoid Mary. A cook for wealthy New England families, she is believed to have unwittingly infected several dozen people in the early 20th century.Although the cause of typhoid fever has been known for over a century, what makes Salmonella typhi so deadly has remained a mystery. Galan and his team showed that the answer to this mystery may be typhoid toxin, a lethal toxin created from the merger of two separate and powerful toxins. …

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Study of oceans’ past raises worries about their future

June 14, 2013 — The ocean the Titanic sailed through just over 100 years ago was very different from the one we swim in today. Global warming is increasing ocean temperatures and harming marine food webs. Nitrogen run-off from fertilizers is causing coastal dead zones. A McGill-led international research team has now completed the first global study of changes that occurred in a crucial component of ocean chemistry, the nitrogen cycle, at the end of the last ice age. The results of their study confirm that oceans are good at balancing the nitrogen cycle on a global scale. But the data also shows that it is a slow process that may take many centuries, or even millennia, raising worries about the effects of the scale and speed of current changes in the ocean.”For the first time we can quantify how oceans responded to slow, natural climate warming as the world emerged from the last ice age,” says Prof. Eric Galbraith from McGill University’s Department of Earth and Oceanic Sciences, who led the study. “And what is clear is that there is a strong climate sensitivity in the ocean nitrogen cycle.”The nitrogen cycle is a key component of the global ocean metabolism. Like the proteins that are essential to human health, nitrogen is crucial to the health of oceans. And just as proteins are carried by the blood and circulate through the body, the nitrogen in the ocean is kept in balance by marine bacteria through a complicated cycle that keeps the ocean healthy. …

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