We focus on concepts and theory for population & evolutionary dynamics, uncertainty & risk, understanding the past and predicting the future.
We study many species including:
tropical understory plants;
NEW PAPER: hurricanes and other extreme events
[From featured topics]
Extreme events significantly impact ecosystems and are predicted to increase in frequency and/or magnitude with climate change. We introduce Generalized extreme value (GEV) distributions for ecologically relevant events, including hurricanes and wildfires,. We show how to downscale a GEV for hurricanes to an ecologically-relevant (~ 10^4 km2) spatial scale and use the results in a stochastic, empirically-based, population model. In a rapidly changing world, our methods show how to combine realistic models of extreme events and of ecological populations to assess ecological impacts, and to prioritize conservation actions for at-risk populations.
NEW PAPER: aging is a traveling wave
[From featured topics]
We show, for five decades in 20 developed countries, that old-age survival follows an advancing front, like a traveling wave. The front lies between the 25th and 90th percentiles of old-age deaths, advancing with nearly constant long-term shape but annual fluctuations in speed. Our unexpected result has implications for biological hypotheses about human aging and for future mortality change.
Blog & In The News
Bloomberg Getting old can be hard under any circumstances, and harder still when you’re poor. That’s the predicament for Thailand, the developing country first in line to face the consequences of a first-world-style baby bust. Data published last month by the United Nations show births in Thailand have dropped to a level on par with Switzerland and Finland, two ultra-wealthy countries with which it has almost nothing else in common.
Live Science Aging is determined by biological, not environmental, factors, a study suggests. No matter how hard you try, it might be difficult to slow down aging, a depressing new study suggests. Across a range of primate species, including humans, aging rates are mostly determined by biological factors, not environmental ones. What's more, the rate of aging is mostly consistent within a primate group. For each primate population, the researchers determined that the "rate of aging seems to be about the same within that group," said Shripad Tuljapurkar, a professor of biology and population studies at Stanford University who helped review the study but was not otherwise involved in it. "That's a pretty significant finding." Still, it may one day be possible for humans to slow down biological aging with medicine, he said.
Economists have been worked up about an “annuity puzzle.” An annuity is bought near-retirement (say at age 67) by giving an insurance company a chunk of money; in return the company guarantees a specified annual income till you die. So annuities should be irresistible to anyone afraid of outliving their money – presumably all “rational” people. The “puzzle” is that very few people buy annuities. Economists have been busy thinking up reasons why people who don’t buy annuities are “irrational.” But most people are actually rational – they just factor in things that economists ignore. What are these factors?
An annuity should free you from return risk (earning poor returns on your money) and longevity risk (outliving your money) – but does it? Most people know that interest on bonds is currently at a historic low, even factoring in low inflation. But today’s annuity prices also turn out to depend strongly on today’s bond returns, which means that annuities are now expensive by historical standards. An annuity paying income of $1 a year now costs around $25 at age 67. Is this price justified?
In the US in 2010, a male at age 67 is most likely to