Oophaga pumilio - Caribbean Slope, Costa Rica

Peering over the Precipice

December 30, 2014 in December 2014

A mass extinction occurs when 75% of the planet’s biodiversity disappears during a relatively brief unit of geological time. Estimates suggest that 95% of past life is now gone and that five prior mass extinctions account for much of this loss. When evaluating the status of biodiversity it is useful to inventory what is present in order to recognize when it is gone. Clearly, this type of inventory is virtually impossible, and while molecular taxonomists are busy counting what is here today, such meticulous work falls into a pattern “one step forward and two steps back.” For example, nearly every careful inventory of a small reef patch, tract of rainforest or microbiota community reveals a new subspecies or species. Metaphorically, the act of counting every existing species is like counting the grains of sand on a wave terraced beach. Much like the waves that deposit and steal grains of sand with each incursion, natural selection alters the genetic composition of one population, while anthropogenic effects eliminate others.

Most who spend their lives studying biodiversity recognize that ours is the era of the sixth mass extinction. With a total of 1,371,500 described animal species, scientists can’t agree on an actual animal diversity count let alone the total number of all species on the planet today. What is known is the following: Of the cataloged vertebrate species on the planet, 26% of mammals, 13% of birds and 41% of amphibians are threatened with extinction. This adds up to short list of 4,529 terrestrial vertebrates. Bear in mind that this number does not include the threatened reptiles and fish nor does it include the countless number of invertebrate species that make up the bulk of animal biodiversity. When statistical estimates of total planetary biodiversity are considered, scientists estimate that 10 to 690 species go extinct every week. Now if this doesn’t make you say “holy shit,” I’m not sure what will.

Thanks nature.com for publishing the linked graphic that illustrates the realities of our biodiversity crisis.

Birch and Beaver Lodge - William Obrien State ParkNikon D800E + Nikkor AFS17-35mm f2.8 — Birch and Beaver Lodge - William Obrien State Park
Nikon D800E + Nikkor AFS17-35mm f2.8

The Shortest Day

December 21, 2014 in December 2014

If you live in the Northern Hemisphere, today is the shortest day of the year. Here, in Minneapolis, sunrise was at 7:48 am and the sun, obscured by the cloud of winter, is setting as I write this at 4:34 pm. While it is common practice to mark the season with Christmas, Hanukkah, Kwanza or the New Year, the Winter Solstice delineates the astronomical transition into next year.

Where's Wisconsin? - St. Croix RiverNikon D800E + Nikkor AFS17-35mm f2.8 — Where's Wisconsin? - St. Croix River
Nikon D800E + Nikkor AFS17-35mm f2.8

If you were a red-necked wallaby, patterns of gestation and oestrus are linked to this annual cycling between long and short days (Tyndale-Biscoe and Renfree, 1987); such responsiveness to daylength is known as photoperiodism. Many biological behaviors can be partially or entirely attributed to photoperiodic changes. When accompanied with shifts in temperature, photoperiodism explains annual biological phenomena like molting, migration, hibernation, reproduction and the development of sexual organs. While not directly related to vision, it should be no surprise to learn that the mammalian response to day length is linked to retinal light-sensitive cells ( http://en.wikipedia.org/wiki/Photoperiodism ).

Late Fall Snow Melt - William Obrien State ParkNikon D800E + Nikkor AFS200-400mm f4.0 VR1 — Late Fall Snow Melt - William Obrien State Park
Nikon D800E + Nikkor AFS200-400mm f4.0 VR1

While the human tendency towards lethargy in winter and promiscuity in summer is probably an evolutionary relic, the astronomical solstice holds deep cultural meaning that extends back to neolithic times. The layouts of archaeological sites like Stonehenge in England and Newgrange in Ireland are aligned with the winter solstice sunset for the former and summer solstice sunrise for the latter. Historical ruins suggest that the early months of winter were linked to periods of famine, and knowledge of this impending loss of daylight had real implications for survival. Punctuated by a final feast, the winter solstice was an opportunity to celebrate life and a good harvest prior to the onset of coldest months. So while everyone around me is busy shopping online and in stores in search of the perfect gift, I prefer to take this time to reflect on the year that was and the year that will be now that the days are getting longer.