Impacts of climate change on biological systems

David B. Lobelldlobell@stanford.edu

Outline:1. Some Basic Principles2. Observed Impacts3. Projected impacts

Several slides taken from NAS report on stabilization targetshttp://dels.nas.edu/Materials/Presentations/Stabilization-Targets

Plants grow better in higher CO2

Photosynthesis: CO2 + H20 sugar + O2

Plants grow better in higher CO2

Photosynthesis: CO2 + H20 sugar + O2

Water use efficiency:

Measuring the CO2 fertilization effect

FACE: Free-air CO2 enrichment (Long et al. 2006)

Plants usually grow worse in higher temperaturesThe main effects of warming:-faster rates of development (see below)-faster rates of photosynthesis and respiration-higher rates of evapotranspiration (important in dry regions)-fewer frosts (important in cold regions)

In a cooler year, this process can take ~10 days longer than in warmer year, which means 10 or more days to photosynthesize

“birth” “adolescensce” “adulthood” “death”

An example: California Almonds

Animal impacts

Food sources changing in quantity, quality, and composition

Many animals affected by loss of sea and land ice

Migratory animals affected by change in seasons

Observed Impacts

(not easy to “observe” impacts)

Option 1: show a big co-incidence of climate and biological changes

Option 1: show a big co-incidence of climate and biological changes

ELAINE: Well, I mean, he was in the apartment, and then it's gone and it's in your apartment.

RAVA: Maybe you think we're in cahoots.

ELAINE: No, no.. but it is quite a coincidence.

RAVA: Yes, that's all, a coincidence!

ELAINE: A big coincidence.

RAVA: Not a big coincidence. A coincidence!

ELAINE: No, that's a big coincidence.

RAVA: That's what a coincidence is! There are no small coincidences and big coincidences!

ELAINE: No, there are degrees of coincidences.

RAVA: No, there are only coincidences! ..Ask anyone!

http://www.seinfeldscripts.com/TheStatue.htm

Option 2: run a model with and without observed climate changes

% Yield Impact

Projected Impacts

Recent and Future CO2 levels

B1

A1b

A2

2 x pre-industrial

Projections for average global temperatures

IPCC, 2007

Average climate model projections of soil moisture change by 2080

IPCC, 2007

Food: Large potential decreases in certain crops and locations

Wildfire in the western US(1-2°C warming)

WesternUS

Ocean Acidification and Corals

Global coral reef distribution and biological production of calcium carbonate skeleton (shell material) taking into account both ocean acidification and thermal bleaching

Photo courtesy of Ove Hoegh-Guldberg

20

And there are also unquantified risks….

22

Can’t separate “biological” and “human” responses to climate change

Farmers and scientists are not dumb

In response to these pressures, people are likely to adapt.

Two main types of adaptations1)Trade2)Management or genetic changes

Human responses to climate change

Cool nations “win”

Warm nations “lose”

1) Trade

One example of estimated impacts for 2x CO2 (from Cline 2007)

Summary

1) Higher CO2 generally helps (except for C4 plants in moist areas)

2) Warming generally hurts (except where its very cold)

3) Precipitation changes are small at global scale, but could be important in some places

4) There are various forms of evidence for observing impacts, none of them perfect

5) Projections tend to focus on things we understand pretty well, but there are lots of things that could change that we can’t really quantify (e.g., what are the impacts of climate change on national security?)

6) For human systems (e.g., agriculture) understanding adaptation is important

Human responses to climate change2) Management changes

Red = no management changes

Green = “adaptation”

IPCC, 2007

Direct effects of climate change-So warming can have some positive and some negative effects.

-The net balance differs depending on crop and location

-Overall, crops in most regions prefer cooler temperatures

Temperature Change (ºC)Yie

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Ch

ang

e (

%) Average Global Yields vs. temperatures, 1961-2002