Kinship groups can have considerable importance (e. g., generational support, inheritance, and information for key life events). During demographic transitions, kinship networks are reshaped by changes in mortality and fertility rates. This paper analyzes consanguineous and female kin and explores the effect on the size and structure of living kin before and after a demographic transition. We compute the kinship network of a female individual with average demographic traits (here called the Focal) at all ages but focus on only demographically dense ages (age 15 to 39).
Tuljapurkar, S., Zuo, W., Coulson, T., Horvitz, C. and Gaillard, J.-M. (2020), Skewed distributions of lifetime reproductive success: beyond mean and variance...
Lifetime reproductive performance is quantified here by the LRS (lifetime reproductive success), the random number of offspring an individual produces over its lifetime. Many field studies find that distributions of LRS among individuals are non‐normal, zero‐inflated and highly skewed. These results beg the question, what is the distribution of LRS predicted by demographic models when the only source of randomness is demographic stochasticity?
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.
Decades of hurricane tracks in study area in S E Florida
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.
Shripad Tuljapurkar was awarded the Sustainability Accelerator award for working on the research and social dimensions of wildlife conservation in the northwest Trans Himalaya. We believe human and natural capital are inextricably linked- not only through shared land-use and ecosystem services but also through their vulnerabilities to processes of change.
Our focus is the high mountains of Spiti and Kinnaur districts in Himachal Pradesh, India, where rapid change is driving a transition from a livestock-dominated production to a system driven by markets for cash-crops and ecotourism. Although cash crops such as green peas and apples have promoted prosperity, they increased local inequality and vulnerability to climate events (drought, landslides).
In this work, we ask how do new risks and opportunities play out against climate change, and impact human livelihoods and human-wildlife interactions? We aim to understand how change in winter precipitation and warming temperatures impact agriculture, livestock rearing and the linkages with biodiversity. We are using crop experiments, models and ethnographic methods to assemble data on time-trends in local agriculture, weather patterns, and the use of ecosystem services with the objective to develop a socio-ecological framework and recommend policy and conservation interventions.
Talk in the Holt Seminar Series as a virtual guest. Professor
Shripad Tuljapurkar holds the Dean and Virginia
Morrison Chair in Population Studies at Stanford. He has made many
distinguished contributions to population ecology, including of plants,
animals and humans, and to evolutionary biology; many of his papers
focus on issues of temporal variability and stochasticity.
"What happens in 20 years?" Tuljapurkar asked the graduate students and postdoctoral fellows attending the workshop. "That is a frightening rate of decline (on fertility rates), especially in smaller countries."