? Day/night and summer/winter temperature changes: minimal in the tropics, high near the poles
The higher the temperature the faster the photosynthetic reaction, provided always that the reaction rate does not exceed the availability of nutrients, CO2, water etc. In general 6°C is the threshold below which very little plant growth occurs.
In Polar climate zones where temperatures rarely get above 6°C there is little growth at any time of year and plants tend to be small and shrubby. In the hotter areas there is year round growth producing much larger plants. In temperate zones there is annual growth with a dormant period happening during the cold winter months.
Land based animal species are dependent upon vegetation, the greater the diversity and quantity of vegetation the greater the diversity of animal life as well.
? Available liquid water: high in the tropics, low near the poles
Many species adapt according to the availability of water. In respect of plants this is often less significant than temperature, for animals the availability of a reliable water source is of paramount importance.
There may be an abundance of water but if it’s cold then cell growth will be inhibited. Equally, plentiful water in a hot climate doesn’t guarantee enhanced growth, if there’s high transpiration then water loss from the biomass can exceed uptake and inhibit growth.
An ideal scenario is adequate year round water supply that exceeds transpiration, something that will occur much more readily in the Tropical regions rather than the Polar ones.
? Fraction of the year above freezing: ~100% in the tropics, probably less than 20% at best near the poles
Overall average annual temperatures: usually around the 80s-90s in the tropics, usually below freezing near the poles.
As per first point.
? Sunlight availability: constant in the tropics, highly variable (and generally lower) near the poles
Sunlight is essential for plant growth but interestingly only a few of the sunniest places on Earth are in the Tropics. The US is fortunate to have five of these places, the other five that make up the top 10 are two places in Egypt, two in Sudan and one in Chad. The Sudanese and Chadian locations are just in the Tropics. Within the Tropics the warming and uplifting of air masses causes quite substantial cloud cover.
Some of the Sunniest places are actually quite cold. Antarctica is one of the sunniest places on the planet and during the spring months Canada is the sunniest place.
The intensity of the Sun is greater on the Tropics and it’s here that we find the areas of highest solar radiation.
Overall the Tropics receive more sunlight and more solar radiation than the Polar regions, along with other factors this aids plant growth.
? Given all that, is it really reasonable to conclude that warmer is necessarily inherently better for biodiversity, rather than being just one possible factor?
The temperature is just one of several factors. The best growth is going to occur when all factors are at their optimum level. If there’s a deficiency or absence in one or more factors then the other factors become irrelevant.
If warmer meant inherently better for biodiversity then Dallol in Ethiopia would be positively thriving with life. It’s not, it’s almost dead. Whilst it’s the warmest place on the planet with high levels of sunshine, the aridity and chemical composition of the ground ensure that very little can either grow or live there.
The claim "The tropics have more biodiversity than the poles, so obviously warmer is better" is an example of how mentally-challenged the low-level denialists here are.
Even Wattsup doesn't try to claim that diversity building up over millions of years of evolution can outweigh mass extinctions happening on a time scale of decades. People who cannot distinguish between absolute and relative percentages, or write English at a high school level, have trouble comprehending the difference between 100 years and 10 million years.
http://wattsupwiththat.com/2012/09/04/wa...
There used to be over 30 million buffalo hanging in the zone halfway between the north pole and the equator, now there are 300 million humans, and all their pets. I would say its the space in between where the real biodiversity exist.
We have had multiple periods of glaciation sweeping most habitats from most of Europe and N. America while the tropics remained relatively unscathed. Most of the habitats in North America were completely different 10 thousand years ago and so those micro-niches (I don't think that is a real word) haven't had a chance to develop. In the tropics, you might have a species of orchid evolve with a species of wasp and they co-evolve with thousands of other specialists in complex ways eventually leading to millions of species. In the places affected by the ice ages, animals and plants tended to be more generalists having to survive in a "diversity" of climates. If we were stable for millions of years, I am guessing that non-tropical areas would develop more diversity.
Diversity by itself isn't necessarily good. You could have increased invasive species which would increase diversity but might cause eventual harm. Generally an ecosystem with decreasing diversity would be an indicator for something being wrong with that ecosystem. Humans have introduced non-native species all over the planet, sometimes with catastrophic results. We have plowed down forests to build cities and farms but that isn't really related to AGW. Those are factors that far outweigh our CO2 emissions IMO.
We sceptics are getting a lot of flak about not being scientists, understanding nothing and contradicting ourselves. Strangely, I see warmists in a similar light.
Take the current question and look at it in this light:
Skeptic: Why is global warming a problem?
Warmist: It will cause the demise of many animal species and reduce bio-diversity.
Skeptic: Where do most animals live: warm place or cool place?
Warmist: Warm place of course.
SkepticL So why do you think warming will reduce bio-diversity?
Warmist: Bio-diversity is not everything you know.
JimZ brings up a good point in that ice cycles of the past limits the time biodiversity can take hold in various regions in the present. If we look at only the tropics though we still see various types of climates. I would take JimZ's point as well as bring in the point of proximity to water.
It's ENSO controlling temperatures Silly. You know it and I know it.
Your question is based on CO2 driving temperatures, which it does not.
ENSO and temperature records are directly correlated.
Warming is definitely happening. The cause is the issue at hand.
What are you going to do if a major La Nina occurs in the next few years? Blame the temperature drop on dimming (from more cloud cover) or dropping CO2 levels?
Your question has nothing to do with Global Warming because it has been clearly shown that warming along with a higher CO2 level causes more bio-diversity and increased life.
This question is rather irrelevant (whether warming is good for bio-diversity) as it is not getting warmer and with the sun heading for another solar minimum, it wont be for a long time.
I see occasional comments from skeptics and denialists on this site along the lines of "The tropics have more biodiversity than the poles, so obviously warmer is better".
But, let's consider, for a moment, the climatic differences between the poles and the tropics, and think about what of them might make a difference in biodiversity.
Day/night and summer/winter temperature changes: minimal in the tropics, high near the poles
Available liquid water: high in the tropics, low near the poles
Fraction of the year above freezing: ~100% in the tropics, probably less than 20% at best near the poles
Overall average annual temperatures: usually around the 80s-90s in the tropics, usually below freezing near the poles
Sunlight availability: constant in the tropics, highly variable (and generally lower) near the poles
Given all that, is it really reasonable to conclude that warmer is necessarily inherently better for biodiversity, rather than being just one possible factor? Any major differences I missed? Any other relevant or instructive comparisons? Any other thoughts?
