Here’s the question: Has any population of organisms (humans excluded) regulated and reduced their population size by lowering their birth rate instead of increasing their death rate? And have any slowed their rate of increase by raising the age at first birth? Most of the examples I know of natural population control do so by increasing the death rate.
Do you mean consciously? Then probably no. But yes for question 1 if you consider dominance hierarchies where birth rates (matings) decrease during reduced resource availability. And yes for question 2 if you consider the example in some small mammals where stress resulting from reduced resources produces pheromones in older females that delays sexual maturity in younger females. Thomas Rosburg, PhD Professor and Chair, Department of Biology Drake Biodiversity Center and Herbarium Drake University, 2507 University Avenue Des Moines, IA 50311 515.271.2768 515.271.2920 cell 515.460.4468 Photo - finish of Leadville Silverrush 50 mile ultramarathon, with daughter Vanessa "Let the rivers run like they always do, its not up to me its not up to you; When we reach the end, when our time is done; Let us all be still while the rivers run" Bob Seger, Let the Rivers Run on Ride Out ________________________________ From: Ecological Society of America: grants, jobs, news <[email protected]> on behalf of Howard S. Neufeld <[email protected]> Sent: Wednesday, January 20, 2016 8:38 AM To: [email protected] Subject: [ECOLOG-L] Reducing Population Size in Natural Populations of Organisms - A Question Hi all - I am currently working on an abstract about global climate change for a regional biology meeting in the southeast, and I wanted to say something about the control of natural populations of organisms, but I am not sure if the statement I want to make is true, so I’m asking for some advice and counsel on this. Here’s the question: Has any population of organisms (humans excluded) regulated and reduced their population size by lowering their birth rate instead of increasing their death rate? And have any slowed their rate of increase by raising the age at first birth? Most of the examples I know of natural population control do so by increasing the death rate. Some further comments: If resources get scarce as populations increase in density then behavioral changes could lead to reductions in the birth rate, but under resource scarcity I would assume that the death rate would go up also. I know about density-dependent and density-independent controls on population growth, but here, I’m looking for explicit examples where populations decrease birth rate without increasing the death rate. You may wonder why I’m asking this. It's because I’m wondering if humans can, in the long-term, reduce their population by lowering the birth rate without increasing the death rate. Yes, some countries are already on that path (Japan, for example), but economists and social and political scientists seem to have a problem with such demographic changes, particularly in a free-market situation where an aging population, even if sustainable, is viewed as less competitive and therefore at risk of losing out (whatever that means) to younger, more dynamic populations. It suggests to me that ecology and society are fundamentally at odds here, and that future societies may require paradigm shifts in the way they operate if humans are to actually create a sustainable society. But that’s another story. For now, I’d be really interested to hear explicit examples if anyone has any. Thanks. Howie Neufeld -- Dr. Howard S. Neufeld, Professor Director, Southern Appalachian Environmental Research and Education Center (SAEREC) Chair, Appalachian Interdisciplinary Atmospheric Research Group (AppalAIR) Mailing Address: Department of Biology 572 Rivers St. Appalachian State University Boone, NC 28608 Tel: 828-262-2683; Fax 828-262-2127 Websites: Academic: http://biology.appstate.edu/faculty-staff/104 Personal: http://www.appstate.edu/~neufeldhs/index.html SAEREC: http://saerec.appstate.edu AppalAIR: http://appalair.appstate.edu Fall Colors: Academic: http://biology.appstate.edu/fall-colors Facebook: https://www.facebook.com/FallColorGuy [http://biology.appstate.edu/sites/biology.appstate.edu/files/imagecache/faculty-photo-full/howieneufeld_June_25-2010_Outside_Rankin_with_Coneflowers.JPG]<http://biology.appstate.edu/faculty-staff/104> Dr Howard S Neufeld | Department of Biology | Appalachian ...<http://biology.appstate.edu/faculty-staff/104> biology.appstate.edu Our Fall 2015 featured faculty member is Dr. Matt Estep. He specializes in Evolutionary Genetics and Genomics. His philosophy of teaching and a short description of ...
