Posts Tagged: lifespan
A Conversation with James R. Carey at Science Café: 'Are There Upper Limits to Human Lifespan?'
Is there a limit to how long we humans can live? Jeanne Calment of France (1875-1997), who died at...
Longer human life spans linked to endangered species loss
It's no big surprise that humans are impacting the planet. But a new study pinpoints a sobering connection.
As human life expectancy increases, so does the percentage of invasive and endangered birds and mammals, according to a study by the University of California, Davis.
Human life expectancy, which is rarely included among indexes that examine human impacts on the environment, surfaced as the key predictor of global invasions and extinctions.
“It’s not a random pattern,” said lead author Aaron Lotz, a postdoctoral scholar in the UC Davis Department of Wildlife, Fish and Conservation Biology when the study was conducted. “Out of all this data, that one factor — human life expectancy — was the determining factor for endangered and invasive birds and mammals.”
The study analyzed data from 100 countries, which included roughly 87 percent of the world’s population, 43 percent of global GDP per capita, and covered 74 percent of the Earth’s total land area. Additional factors considered were agricultural intensity, rainfall, pesticide regulation, energy efficiency, wilderness protection, latitude, export-import ratio, undernourishment, adult literacy, female participation in government and total population.
The findings include:
- New Zealand, the United States and the Philippines had among the highest percentages of endangered and invasive birds.
- New Zealand had the highest percentage of all endangered and invasive species combined, largely due to its lack of native terrestrial mammals. The study said that in the past 700 to 800 years since the country was colonized, it has experienced massive invasion by nonindigenous species, resulting in catastrophic biodiversity loss.
- African countries had the lowest percentage of invasive and endangered birds and mammals. These countries have had very little international trade, which limits opportunities for biological invasion.
- As GDP per capita — a standard measure of affluence — increased in a country, so did the percentage of invasive birds and mammals.
- As total biodiversity and total land area increased in a country, so did the percentage of endangered birds. (Biodiversity in this context is not a measure of health but refers to the number of species in an area.)
Lotz said the study’s results indicate the need for a better scientific understanding of the complex interactions among humans and their environment.
“Some studies have this view that there’s wildlife and then there’s us,” said Lotz. “But we’re part of the ecosystem. We need to start relating humans to the environment in our research and not leave them out of the equation. We need to realize we have a direct link to nature.”
The study was featured in the Los Angeles Times, Wired, and the U.K.'s Daily Mail among other media.
/span>Lifespan
Annuals: one growing season; biennials: two growing seasons; perennials: many growing seasons. As gardeners, we know what to expect from our plants. Trees? Trees live forever, right? Nope. The fact that a tree may outlive a human is not disputed. There are dozens of ancient historical oak trees (Quercus spp.) that are several hundreds of years old, the “General Sherman” giant sequoia (Sequoiadendron giganteum) is nearly 3,000 years old, and “Methuselah” is a Great Basin Bristlecone Pine (Pinus longaeva) aged at more then 4,800 years and according to Wikipedia, is the oldest living organism on the planet.
With all those ancients in mind, I understand why we are perplexed when a tree dies. Especially when it is a relatively young tree. My colleague Kathy Thomas-Rico wrote recently about the death of European white birch trees (Betula pendula) in Vacaville. (“Birch Issues,” Under the Solano Sun, 9-2-11). It hit home this summer, right in our front yard. Our birch began to look less leafy than normal and subsequently died. Our tree was one of many planted by the developer that built the homes on our street. Over the last sixteen years our tree grew to about thirty feet tall and except for nearly all the branches being on one side due to the prevailing Solano wind, it seemed healthy. I have since learned that the European white birch is not suited to our growing zone, which is too dry and too hot. It is even considered a weed by the U.S. Forest Service - one gardener’s shade is another’s invasive species!
Over the last few years we have watched the birches disappear one-by-one from the neighborhood. I am sad our pretty white birch has been reduced to little more than a perch for the wild birds, which is still a pleasant purpose, just not the intended one. But it serves as a reminder that trees have a lifespan.
What We Can Learn from Insects
What can we learn from insects? Lots. But first, let's talk about the UC Seminar Network. It's a...
James R. Carey