Time-transgressive changes in forest

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Past Abrupt Changes in Climate and Terrestrial
Ecosystems
Jack Williams
University of Wisconsin-Madison
Kevin Burke
University of Wisconsin-Madison
Matt McGlone
Landcare Research, New Zealand
Barry Carlsen
@IceAgeEcologist
HiRes Workshop, June 1-3, 2015
Rapid Rates of Climate & Ecological
Change: Two distinct sets of risk
Species Rate of Response >> Climate Change
 Adaptive lags; heightened extinction risk, may require
management intervention
Species Rate of Response >> Rate of Climate
Change
 Tipping points, regime shifts, ecological surprises
Even slowest IPCC scenario is faster than
anything in history of human civilization
Holocene annual(?) temperature
trends
Holocene: ~0.8ºC cooling
RCP2.6 (low): 0.7-1.7ºC
Marcott et al. 2013 Science
IPCC 2013 AR5 WGI Chap. 12 Fig. 12.5
Projected changes in global mean
temperature by 2100AD
How do we manage ecosystems
experiencing rates of change we’ve
never seen?
Can species keep up?
Species movement capabilities vs. climate velocities
IPCC 2013 AR5 WG2 Fig. SPM
Complex systems may have tipping points,
alternative stable states, rapid regime shifts
Mean annual rainfall (mm)
Scheffer & Carpenter 2003 TREE; Staver et al. 2011 Science
Abrupt Changes Common in the Past
PETM
Last deglaciation
PLEISTOCENE || HOLOCENE
Zachos et al. 2005 Science, Rahmstorf 2003 GRL,
Grootes et al. 1993 Nature, Booth et al. 2012 Ecology
DO Events
Holocene tree collapses
Causes of past abrupt ecological changes
1) Strong extrinsic forcing
(hammers),
2) Tipping points, thresholds,
and other feedbacks
intrinsic to ecological
systems (canoes)
3) Feedbacks with other earth
system components (loops)
Precipitation
Rates
Tropical Tree
Density
Photo: The Destruction Company
http://www.luxuo.com/membership/the-destruction-company.html
Transpiration
Rates
Each lets us answer different questions:
How quickly can ecological systems
respond to rapid climate change?
Where are the tipping points and
tipping elements in ecological
systems? Can we develop early
warning signals?
What are the relative contributions of extrinsic and intrinsic
processes to past abrupt changes?
Photo: The Destruction Company
http://www.luxuo.com/membership/the-destruction-company.html
Extrinsic Forcing Case Study: Vegetation
Responses to Last Deglaciation
Temperature Variations Since the LGM
Large Climatic Forcing:
• Global temperature: rose ~5ºC
• Abrupt regional change: 915ºC in 5-60 yrs
PLEISTOCENE || HOLOCENE
Large Biotic Responses:
(Grootes et al. 1993 Nature)
• Species ranges shift by 102 to 103km
• Reshuffle into no-analog communities
21,000
15,000
11,000
7,000
Modern
Spruce
Pollen
%
Ice
Ice
%
Ice
%
%
No Data
Williams et al. (2004) Ecological Monographs
How fast did tree species respond?
Gerzensee,
Allerød warming
Pinus arrives
(800 years)
Juniper expands
(<8-16years)
Ammann et al. 2013 P-Cubed
Meerfelder Maar,
YD cooling
Windiness
increases &
Tundra expands:
(no lag)
YD onset at
Greenland
Rach et al. 2014 Nat. Geo.
Kråkenes Lake,
Holocene warming
Betula arrives:
(700 years)
Heath expands
(250 years)
Artic flora collapse
& Salix ↑ (no lag)
Birks 2015 Holocene
Intrinsic Tipping Points: Vegetation Responses to
Holocene Aridification
North Africa:
• Aridification between 9ka and 5ka
• Grassland ->Desert
• Abrupt and time-transgressive local
changes
North American Great Plains:
• Aridification between 11ka and 6ka
• Forest->Prairie, Dunes activate, etc.
• Abrupt and time-transgressive local
changes
Hoeltzmann et al. 1998 GBC
Photo credit: Joe Mason
North Africa
•
•
•
•
Gradual insolation forcing
Regional aridification 9ka to 5ka
Locally abrupt changes
Time-transgressive & rapid local
declines in rainfall
• Differential & rapid collapses of
species within sites
Time-transgressive changes in hydrology
Shanahan et al. 2014 Nature Geo.
North Africa
•
•
•
•
Lake Yoa
Gradual insolation forcing
Regional aridification 9ka to 5ka
Locally abrupt changes
Time-transgressive responses
across sites
• Differential timing among taxa
within sites
Kropelin et al. 2008 Science
Great Plains: Similar to North Africa
• Gradual insolation forcing
• Regional aridification 11ka to 6ka
• Multiple System Responses:
• Dunes activate,
• C3->C4 grasslands,
• Forest->Prairie,
• Lake levels drop
• Locally rapid and time-transgressive
Time-transgressive changes in forest->prairie
shifts
Williams et al. 2010 Geology
Summary
1. Two distinct risks for ecological systems during rapid 21stcentury climate change:
A.
B.
Failure of species to keep up with rapid climate change
Tipping points and ecological rates of response much faster than
environmental forcing
2. Many past abrupt events, caused by rapid extrinsic forcing,
intrinsic tipping points, and vegetation-atmosphere
feedbacks
3. Last deglaciation: Fast and slow vegetation responses to
abrupt climate change: near-zero to centuries
4. Holocene aridification: regionally slow, locally abrupt.
Caused by ecological tipping points? Can we model this?
5. Need more study of paired high-resolution studies of abrupt
climatic & ecological change
Thanks & Acknowledgments
Matt McGlone & Kevin
Data Contributors Brigitta Ammann, Hilary Birks, Achim Brauer, André
Lotter, Oliver Rach, Tim Shanahan, Willy Tinner, and Willem van der
Knaap
Funding and Infrastructure:
NSF
Neotoma Paleoecology DB
Bryson Climate, People, &
Environment Program
Further Reading:
Williams, J.W., Blois, J.L., & Shuman, B.N. (2011) Extrinsic and intrinsic forcing of abrupt ecological change:
Case studies from the late Quaternary. Journal of Ecology, 99, 664-677.
Williams, J.W. & Burke, K. (in press). Past abrupt changes in climate and terrestrial ecosystems. In Climate
Change and Biodiversity (eds T. Lovejoy & L. Hannah).
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