Transcript Ecosystem Impacts

Impacts of climate change on
biological systems
David B. Lobell
[email protected]
Outline:
1. Some Basic Principles
2. Observed Impacts
3. Projected impacts
Several slides taken from NAS report on stabilization targets
http://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 temperatures
The 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)
“birth”
“adolescensce”
“adulthood”
“death”
In a cooler year, this process can take ~10 days longer than in warmer
year, which means 10 or more days to photosynthesize
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
A2
A1b
2 x pre-industrial
B1
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)
Western
US
Ocean Acidification and Corals
Photo courtesy of Ove Hoegh-Guldberg
Global coral reef
distribution and
biological production
of calcium carbonate
skeleton (shell
material) taking into
account both ocean
acidification and
thermal bleaching
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 adaptations
1) Trade
2) Management or genetic changes
Human responses to climate change
1) Trade
Cool nations “win”
Warm nations “lose”
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 change
2) 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
Yield Change (%)
-Overall, crops in most regions prefer cooler temperatures
Average Global Yields vs. temperatures, 1961-2002
Temperature Change (ºC)