Thursday, March 21, 2013

Population Size =/= Consumption

     As Matt talked about in class and I previously mentioned in this blog, one of the major causes behind conservation issues is human population growth and consumptive demand. In December 2012, an editorial was published in Conservation Biology discussing just that (Allendorf & Allendorf 2012).

     It was short, succinct and well written. It explained the causative factors behind the population boom of the past two centuries and how it will end within 100 years. Their view of the future was a reasonably positive one as they provided concrete ideas on how we can address population growth and consumption now in order to minimize conservation issues in the future.

     According to the editorial, the human population became an environmental problem only in the past 150ish years. Prior to the 1800s, mortality and fertility was high. People lived to an average age of 35 and each woman had on average 6 children. The world’s population was about 1 billion with a minimal environmental impact.

     Then in the 1800s and 1900s, medicine and hygiene improved. People began to live longer and their children had better chance of having kids of their own. Fertility rates began to fall from 6 to 2.5 kids per woman. According to the article, fertility levels stabilized in the late 1800s in developed countries and around 1950 in others. Because women could be reasonably sure their kids would survive to adulthood, they gave birth fewer times.

      By the early 1960s population growth rate peaked. This means that while the world’s population is still rising but it isn’t growing nearly as fast as it once was.

     With regards to the future, the authors suggest that population growth will peak by 2100 at around 10 billion. Furthermore as fertility rates are lower now than in the 1700s, it is likely that the world’s population will decline slowly throughout the 22nd century.
The authors seem to be describing the trend shown here...
     The authors also provided suggestions to deal with conservation issues by addressing the root cause of population growth and over-consumption:
     1)      Support family planning and contraception. This will help women control the number of children they want to have, and in turn minimize population growth.
     2)      It is not population size but spatial distribution that matters – therefore work to concentrate populations in centers away from sensitive environments.
     3)      Consumption is not correlated with population size but rather with the number of population ‘units’ (households) present. Therefore seek to reduce consumption by providing social and economic benefits to these population ‘units’. Make consumption reduction matter.

     I found these suggestions intriguing. The idea that it’s not the number of people that matter but where they are and how they organize themselves is interesting – consumption is independent of population size.

     Furthermore their prediction that populations will stabilize and even decline, it changes our perspectives on conservation. I think dealing with a constant predictable pressure would be better than the endless upward trend we are experiencing now.



Allendof, T. D., and K. Allendorf. 2012. What Every Conservation Biologist Should Know about Human Population. Conservation Biology 26:953-955.

Wednesday, March 6, 2013

Lyall's Mariposa Lily




Lyall’s Mariposa Lily, AKA Cat’s Ear Lily
Calochortus lyallii


I first heard about this species of Mariposa lily in first or second year; I cannot remember which. It was mentioned just as a passing comment by a professor (Lyn, I think), about there being a rare variation on the Sagebrush Mariposa Lily that is so prevalent in the grasslands around Kamloops. Apparently it only grew down south by the border – in the Boundary region perhaps, or maybe down in the Okanagan.

This past summer I spent two months taking soil samples in the grasslands throughout southern BC. Once we started sampling in the Okanagan, I kept my eyes peeled for this lily, much to the chagrin of my field partner. At the time, the Sagebrush Mariposa lilies were in full bloom and spectacular… but I never once saw Lyall’s Mariposa lily.  

One day we were heading to two sampling sites very close to the Canada-US border – one was on the south side of Kruger Mountain, the other was on the south side of Black Mountain. We managed to get to the Kruger Mountain site easily enough, but on the way to the Black Mountain site the road was flooded so we turned around. The next day we drove on to the East Kootneys and I looked no more for this beguiling plant.


I did not think again of the Cat’s Ear lily until a few days ago when I found an entry in the eFlora BC database (Klinkenberg 2013). Like most of the plants on eFlora, a map is provided showing the GPS coordinates where the species has been observed in the past. On it I zoomed in… and saw that one of the only places in all of BC (and for that matter, all of Canada) that this species is found is on the south side of Black Mountain. In the Chopaka region of the Okanagan-Similkameen. Less than 50 meters up the hill from where we turned around this summer.

I was so close and yet so very far away!

 
I suppose why I am sharing this story of hunting and not finding this lily is because as a species, it raises a unique conservation question.
In all of Canada, there are only five populations of Lyall’s Mariposa lily, scattered on and around this one small mountain in the Southern Okanagan. Because of a small population size and threats from cattle grazing, this species was listed by COSEWIC in 2001 as threatened (Klinkenberg 2013, Miller 1999).
However, it is very abundant further south in Washington and Oregon, so the species won’t be extinct if the population on Black Mountain dies out. But the Black Mountain population is ours; it is Canadian.

Therefore, how do we approach the conservation of this species given that in Canada it is endangered, while throughout the entirety of North America it is doing quite fine (Encyclopedia of Puget Sound 2011)?

Should we act to conserve this species or not? How do we decide?



Miller, M. T., and G. W. Douglas. 1999. Status of Lyall’s Mariposa Lily, Calochortus lyallii (Liliacaeae), in Canada. Canadian Field-Naturalist 113:652-658.

Klinkenberg, B. 2013. Calochortus lyallii Baker. E-Flora BC: Electronic Atlas of the Plants of British Columbia, University of British Columbia, Vancouver. Available from http://linnet.geog.ubc.ca/Atlas/Atlas.aspx?sciname=Calochortus%20lyalliii.

Encyclopedia of Puget Sound. 2011. Calochortus lyallii. Puget Sound Institute. Available from http://www.eopugetsound.org/species/calochortus-lyallii