Download Lessons for ecology, conservation and society from the Serengeti

Lessons for ecology, conservation and society
from the Serengeti
Anthony R.E. Sinclair
Centre for Biodiversity Research
University of British Columbia, Canada
THANK YOU
Dr. Simon Mduma
Head of TAWIRI &
the Serengeti
Biodiversity Progam
The Macaulay Institute
Frankfurt Zoological Society
NSERC, Canada
National Geographic Society
Wildlife Conservation Society
THE TEAM
Simon Mduma
Stephen Makacha
Ally Nkwabi
John Mchetto
Anne Sinclair
John Fryxell
Ray Hilborn
Roy Turkington
Kris Metzger
and indirectly
Markus Borner
Simon Thirgood
and many others
THE WORLD PROBLEM
Species are being lost at unprecedented rates.
How much can we lose before the ecosystems in which
we live become unsustainable?
Species exist within a matrix of other species
and are subject to the effects of their environment
We must understand how the whole system behaveslack of understanding could lead to surprise,
inappropriate management, or even system collapse
THE NEED
- therefore, one must understand important
properties of ecosystems to apply
- effective management
- effective conservation
Changes in Ecosystems can lead to
unexpected outcomes
Flathead Lake, Montana
Opossum shrimp added to provide
extra food for
Kokanee Salmon
Bald eagles
Flathead lake, Montana
Bald Eagles x 7
160
Kokanee x 1000
140
Opossum shrimp
Abu n d an ce In d ex
120
100
80
60
40
20
0
1978
1980
Spencer et al. 1991 BioScience
1982
1984
1986
1988
1990
Unexpected events occur because of
complex interactions.
Illustrated by events in Serengeti, Tanzania
The Serengeti Ecosystem
ia
Loita
plains
Rift v
al
ley
KENYA
uva
Old e
g
gor
i
TANZANIA
2942
ley
Serengeti
plains
Gelai
Salai
2962
plains
Ol Doinyo
Lengai
Ketumbaine
Meru
4565
Rift v
al
r
Isu
p
ar
c
S
From Grant Hopcraft
SERENGETI IS COMPOSED OF TREELESS PLAINS
..AND SAVANNA WOODLANDS
Wildebeest is the dominant species
Wildebeest migration patterns
TANZANIA
KENYA
The reason
for dry season
migration
Mean Annual Precipitation
1200
Kris Metzger
400
SNP Boundary
Mean Annual Precipitation (cm)
36 - 46
46 - 55
55 - 64
64 - 73
73 - 83
83 - 92
92 - 101
101 - 111
111 - 120
No Data
40
0
40
80 Kilometers
Population Size (x 1000)
Serengeti Wildebeest Population outbreak –
the event that changed everything – to
understand it we must go back a century
1800
1500
1200
900
600
300
0
1950
1960
1970
1980
1990
2000
The Great Rinderpest
•
•
•
•
•
The Epizootic of 1889
Ethiopia to Cape by 1896
Die-off of cattle and other ruminants 95%
These include African buffalo
Wildebeest yearling disease present up to
1963
• THIS IS THE PERTURBATION THAT UNDERLIES
OUR UNDERSTANDING OF THIS SYSTEM
% with Antibodies
Incidence ofRinderpest
Rinderpest in Serengeti
100
Wildebeest
80
60
40
Buffalo
20
0
1955
1960
1965
Years
1970
Complex events that followed the wildebeest increase
- Grass fires: between 1920s and 1960s 80-90% of savanna
was burnt each dry season
Grass fires prevent tree regeneration below 2 m height
Repeated burning prevents regeneration and produces
a distorted age structure of old trees
% Acacia Canopy
% Acacia tree canopy cover drops rapidly in
the 1960s
H.Dublin 1986
30
25
20
15
10
5
0
1940
1960
1980
Year
2000
Northern Serengeti, Mara triangle 1944
Photo Syd Downey
1983
Wildebeest grazing reduces grass fuel and area burnt
% Area Burnt
SERENGETI AREA BURNT IN DRY SEASON
100
90
80
70
60
50
40
30
20
10
0
1960
1970
1980
1990
2000
Increase in wildebeest causes decrease
in burning
100
% area burnt
80
60
40
20
0
0
500
1000
Wildebeest number (thousands)
1500
Complex interactions of wildebeest and
the environment
The extent of grass fires is determined by the
degree of grazing imposed by wildebeest
….this had consequences on savanna trees
1980
1991
Savanna
1986
2003
Martin and Osa Johnson 1928
Osa Johnson filming from plane 1933
NYARABORO FROM EMAKAT
1982
1928
2003
SERENGETI TREE DENSITY
rate of change in trees
0.6
Instantaneous rate of change in tree density
negative 1920s-1960s, then increases rapidly
in 1980s, 1990s following wildebeest
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
-0.2
1920 1930 1940 1950 1960 1970 1980 1990 2000 2010
Lions use thickets to capture prey
- more thicket improves success
Serengeti woodland lion numbers
increase in the 1990s
lion
350
1600
wildebeest
1400
300
Lion number
1000
200
800
150
600
100
400
50
200
0
1955
0
1960
1965
1970
Lion data from C. Packer
1975
1980
1985
1990
1995
2000
2005
Wildebeest x 1000
1200
250
Decrease in most resident prey
50,000
12,000
impala
topi
10,000
40,000
Topi number
Impala number
8,000
30,000
6,000
20,000
4,000
10,000
2,000
0
1970
0
1975
1980
1985
1990
1995
2000
2005
Disturbance and multiple states
Ecosystems are continually being disturbed
weather events
human harvesting
invasions of species
predation
Disturbance can cause a change of state
Disturbance changes ecosystems – which do not
always return to the original state afterwards
The role of elephants in Serengeti
Elephants knock down mature trees and
blamed for tree decline
Trees and elephant predation
1970s – fire rather than elephant shown to be
the cause of decline (Norton-Griffiths work in 1970s)
Elephant play another role by feeding on seedlings
Dublin observed elephants removing almost all seedlings
- They hold the system in a grassland state
Removal of elephants in Serengeti by ivory
poachers in 1980s but not in Mara…..
SERENGETI ELEPHANT
POACHING
3500
3000
IVORY
BAN
Number
2500
2000
1500
1000
500
0
1950
1960
1970
1980
1990
2000
2010
..resulting in much food for elephants in the 1990s and 2000s in
Serengeti but not the Mara (wildebeest in both)
SERENGETI - MARA 2005
-hence ecosystems can have more than one state
under the same conditions
TANZANIA
KENYA
Tibetan yak
Tibetan grasslands near Naqu
MONGOLIA – Brandt’s vole outbreaks
12
Number of outbreaks
10
8
6
4
2
0
0
2000
4000
6000
Livestock equivalents
8000
10000
CHANGE IN STATE:
swans on Lake Ellesmere, New Zealand
80000
Number of swans
70000
Wahine Storm, 1968
60000
50000
40000
30000
20000
10000
0
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
Disturbance and Ecosystem Processes
What goes wrong if we ignore
ecosystems? Their processes for
ecosystem functioning
For example
• Hydrology, flux and storage
• Biodiversity and Stability (resilience)
Saline upwelling in Western Australia
Biodiversity and stability
• species diversity and community
resilience
e.g. Australian Eucalypt woodlands
Original closed
eucalypt
woodland
Degraded eucalypt woodland
Loss of bird diversity in Australian woodland
Noisy miners reduce or exclude…..
…white-plumed honeyeaters and other
species in degraded Eucalypt woodland
Drawings Frank Knight
Psyllid outbreaks
in isolated trees
of farmland
Psyllid insect outbreaks cause dieback in exposed trees
-disruption of intact forest causes biodiversity loss and
ecosystem disfunction
Eucalypt dieback – eastern Australia
Long time scales - The effects of history
Disturbance events take a long time
To understand ecosystems we must understand
the long-term events. History is important
Rinderpest – the ecological event in 1889 that
changed the course of human history in Africa.
It decimated human populations and allowed
the colonization of Africa
The ecological effects are still seen in Serengeti today
Buffalo long-term
change 1890-2003
Poaching
80000
Observed
Reported
70000
Number
60000
50000
40000
The Great
Rinderpest
epizootic
removed
30000
20000
10000
0
1890
1910
Data from Sinclair & Mduma
1930
1950
1970
1990
2010
Acacia tree density 1880-1980
6
Log Frequency
5
4
The great
rinderpest
3
2
1
0
1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980
Disturbance and
history
THE IVORY
TRADE
1840s – 1890s
TIPPU TIP
The great slave
trader of eastern
Africa
- 1860s to 1890s
EAST AFRICAN IVORY EXPORTS
Ivory from Zanzibar
Ivory from Khartoum
350
250
300
kg x 1000
kg x 1000
200
150
100
250
200
150
100
50
0
1840
50
1860
1880
Data from C. Spinage 1973
1900
1920
0
1840
1850
1860
1870
1880
1890
1900
SERENGETI ELEPHANT
Poaching
3500
3000
counts
CITES
Ivory ban
reports
2500
Number
The Ivory trade
2000
1500
1000
500
0
1850
1900
1950
2000
The effects of history
Ivory hunting – affected the vegetation in
Protected areas such as Tsavo (Kenya) and
Chobe (Botswana), and altered the long-term
course of conservation in Africa.
It also decimated human populations and
prevented human advancement
Disturbance and history
Therefore,
- ecosystems are always changing,
- they do not return to the same state
- long-term consequences
- e.g. Scotland
- e.g. New Zealand
LESSONS FOR SOCIETY: THE FUNCTION OF
MIGRATION
Migration allows use of ephemeral resources on the
plains and so larger populations than if they were
resident. This rule applies to all migrations
Traditional Human
migrations in the
Sahel follow rain
SAHEL
Boreholes have been sunk in the Sahel since the 1960s to
present. Sedentary life style has resulted in overgrazing
.. and repeated famines. MALI FAMINE 1973
Photo A. de Vos 1975
MALI –
The
Green Polygon
1973
demonstrates
overgrazing
not drought
The ranch
boundary
The role of Protected Areas
-
The Green Polygon illustrates the need for baselines
-
Protected Areas act as such ecological baselines
to provide insight for human ecosystems
-
BUT Ecosystems are continually evolving and do not
return to where they began
-
Protected areas will not stay as they are currently
Take home message
Conservation has to focus on ecosystems
- they are complex, have long time scales and
multiple states
- they are subject to disturbance which can change state
- human disturbance can be monitored by reference to
Protected Areas
- ecosystems are continually changing
Current protection strategy is not addressing this issue
- we need to find a new way to accommodate change