October 30, 2007
Biological Impact of Global Change
We want to go from looking at the period of time from the last glacial maximum to the present.
During the Holocene we will look at. The types of things that happened to populations and make
projections that will happen because of the doubling of C02.
I will go back to biology 101 to familiarize yourself to think about species moving in response to
major climate change. In the case of the past it would be deglaciation and now significant warming.
(Reads – Wallace Broecker, Cooling the Tropics, 1995) You are working with an incredibly sensitive
system when working with the atmosphere.
(Reads – T.S. Eliot 1888-1965) That seems fairly complicated but it summarizes nicely the Paleo
climatic record to the future. You guys are the future.
Ecology 101: The first thing to think about when talking about species distribution is that each is
unique in terms of their requirements. The niche is the profession of the species. It is how it makes it
living and who it interacts with (predators etc.) It is the totality of its life.
Remember for species they are faced with all sorts of environmental parameters not just temperature
and moisture. Example species 1 can live at higher moisture and higher temperature whereas species
2 can live at lower moisture and lower temperature. Example: You are a white tailed deer and they
live in the Eastern Deciduous forests and they can live quite happily most of the time. If we get 1 ½
metre of snow they are dead. You only need 5 or 10 days with really deep snow and that will kill
them. They don’t invade Algonquin Park because of this. It isn’t the means it is the extremes. They
have to get past extremes or they die. It is the extremes that are important. This illustration of a
Niche can be extended to 3 variables like volume but you don’t know which one is important. All
together they are called a hypervolume. Together it is the fundamental niche of a species and that
defines where the species can live. The niche of a species can overlap with that of another but it can’t
overlap totally. They can’t be exact in the same niche because of the competitive exclusion
principle. This says that where two species do the same thing then one will be excluded because of
competition. We don’t compete for oxygen but for critical items if competing seriously then one
survives and the other doesn’t.
The other thing to think about is that this idea of tolerance ranges. Here you have the tolerance zone
and again I have to emphasize the importance of life stage of an organism. We are adults and very
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robust to insights but if you are a baby you can’t. If the environment isn’t suitable the adult will
survive and the baby will not. You have two zones, dark blue is optimal and light blue is marginal, so
if this is an area within the geographical range of the species then site A falls completely within the
temperature moisture gradient and so does B. For C and D a portion of the variation falls outside
their zone. So portions are suitable but not all the time so this is the extreme idea I mentioned.
This gives the niche space for this bird called the blue-grey gnatcatcher. They forge at different
heights but this shows the tolerance and the optimal height that they can eat. Why not go to the top of
the tree? There is competition and predators. Here we have Cooper’s Hawks and they will just pick
off the smaller birds.
This shows the Loblolly pine tree. The dash line shows the natural limits and this purple line is the
calculated limits. IN trying to project you have to understand how this pine species will respond in
the new environment that is coming.
The same thing goes for birds. Here you see the Eastern Phoebe and we have it here in the summer.
They catch flies by sitting on the end of a branch and waiting until they fly by to catch them. The
bold blue line marks the edge of the winter range. Isotherm is the zone of equal temperature across
The other thing to think about is the problem of ecotypes. Within a species there may be a number of
different races and each race is adapted to a unique environment. They may interbreed but they cope
with unique environmental conditions of a particular site. What might happen with climate change?
If you look at initial time and the geographical range of the species (blue -> green -> yellow -> red)
and each is an ecotype. You can’t assume that within a species everybody has the same genetic
compliment. They can do everything everywhere and this is very important. With climate change
species will have to move and have to move into areas where they may not be genetically adaptable.
So their environment shifts at each time change and note that there are two axis and it shifts up to the
upper right. The only ones that can survive in this new environment is the genotype with that
particular configuration so you lose all the other genetic variation. So if you think of glaciation and
deglaciation this continuous back and forth had to result in a lot of loss of genetic variation.
Types of things that might change – we expect populations to go north and south of the equator but
what changes might happen to which they have to adapt to? The critical thing that changes is light.
Equator you have 12:12 hours (light/dark). So how do 1 million Wildebeest get together to breed
within 5 days? By the moon. If you go into the woods right now the white tailed deer males will be
breeding. I had a student walking out to my research trailer and a buck (male deer) chased him. It hit
the door of the trailer. All they think about are females right now. They are synchronized to this
latitude and the time giver is light. They know the light is decreasing and they know to shift the
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velvet and constrict the blood to the antlers and they go into the breeding mode. Look at Dandelions;
they bloom in spring but what happens if they have to move further north? I worked in the Arctic and
it didn’t matter when I went to bed it was always sunlight in June and July. In the Southern Yukon at
11:00 or 2:00 in the morning we can work. In Nunivak they play baseball at 2:00 in the morning. So
the photo period is critical and if you can’t adapt to that to breed then there is a problem. This
variation is important to deal with photo period.
The top portion of the graph is screwed up but it is a classic experiment on the Yarrow plant. He took
seeds along the elevation gradient and grew them in a common garden. He asked ‘do they retain the
biological characteristics of their source population?’ He found that they didn’t. They have intense
solar radiation because they are lower down but they retain the same characteristics. These numbers
indicate the number of days and plants that they don’t flower. For this variety 34 of the plants didn’t
Models of Community Organization
In addition you are working communities of plants not individual plants. It is being tested by time.
Are they doing their thing independently or like a big body? If you pull a pine out of a forest does the
whole system collapse? There was a view like this (overhead) but is there any evidence of that in the
real world? Are communities like organisms and we just happen to get together because of
environmental variables at the time? What is the answer? If you had to put your money on the two
models (a or b) what is the answer? How is the world constructed biologically with respect to
communities? The answer is b. Remember the past has been hard on individuals and plants so they
are probably not moving together as a group. So the individualistic continuum model is the one
that is correct as to how communities are organized, they are not organized like a body.
This shows the distribution of trees and this shows the % of the community that has these 3 species.
They go up the elevation gradient and as you go up one is dominant and the others drop off but they
don’t do it as a unit. There is an overlap.
This second chart is also 3 different species and it is the same picture. They overlap and they are not
nice sharp boundaries.
Three Extinction Mechanisms
These are three mechanisms by which species can go extinct so this is very important. We think
extinction will be a major problem in the next 100 years. Communities will disappear and also the
species associated with them.
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We want to go from looking at the period of time from the last glacial maximum to the present. The types of things that happened to populations and make projections that will happen because of the doubling of c02. I will go back to biology 101 to familiarize yourself to think about species moving in response to major climate change. In the case of the past it would be deglaciation and now significant warming. (reads wallace broecker, cooling the tropics, 1995) you are working with an incredibly sensitive system when working with the atmosphere. (reads t. s. Eliot 1888-1965) that seems fairly complicated but it summarizes nicely the paleo climatic record to the future. Ecology 101: the first thing to think about when talking about species distribution is that each is unique in terms of their requirements. The niche is the profession of the species. It is how it makes it living and who it interacts with (predators etc. )