Science Monday

Though it may seem a no-brainer that increased damage to forests from bark beetles makes them more susceptible to forest fires, there is no general consensus in the published research on what role beetle damage plays. Bark beetles do affect the fuels available to fires and the behavior of those fires, but huge gaps in the scientific knowledge mean it is still impossible to make general conclusions about the beetles’ impacts on fires. Those are the findings of a recent report analyzing past studies, which have reported a range of sometimes contradictory conclusions.

A few consenses emerged in this review, however. For instance, once the needles of a bark-damaged tree have faded to red, the probability of a crown fire — the type of fire that jumps from treetop to treetop — increases, though the probability of a surface fire does not. Factors such as increased wind speed resulting from a more open forest canopy following beetle damage can also increase fire likelihood and severity, though many non-beetle-related factors, such as past forest disturbances, type of vegetation and topography, are still more important factors than beetle damage.

But the primary conclusion of the report was that much more research is needed to fill in the gaps in knowledge and clarify the many preliminary or contradictory conclusions that currently exist in trying to understand the effects of the widespread beetle damage on increasingly widespread fire outbreaks.

■ It has been fairly well-documented that high biodiversity can help protect against the spread of many diseases, but not much was known about how the diversity of the parasites that can spread those diseases affects that calculus. But a new study from University of Colorado researchers, released earlier this spring, found that, for amphibians, an increase in the diversity of parasites in a pond causes a decrease in the rate of successful infections. Examining threats to amphibians is particularly important, as amphibians are one of the fastest declining groups of animals on the planet due to the spread of diseases and other factors. The study found that an ecosystem rich in biodiversity, including that of parasites, meant that the parasites had to compete against each other, making it more difficult for virulent ones to infect amphibians.

■ A study trying to determine what type of salad dressing maximizes the amount of nutrients one absorbs from a salad found that dressings composed of monounsaturated fats were best. Participants more effectively absorbed carotenoids, such as lutein or beta-carotene, which are associated with many health benefits, from the vegetables and greens when they were dressed with a monounsaturated fat such as canola oil than when they were dressed with a polyunsaturated fat like soybean oil or a saturated fat like butter.

■ The latter two also increase absorption of nutrients, but they require more fat in order to get the same nutrients. Low amounts of a monounsaturated fat, on the other hand, promote the same absorption of nutrients as higher amounts, the study found. Those who choose fat-free dressings would get fewest calories, of course, but they would also get fewer of the benefits from the vegetables in the salad.


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