Upload
hieu
View
24
Download
0
Tags:
Embed Size (px)
DESCRIPTION
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 - PowerPoint PPT Presentation
Citation preview
Lessons for ecology, conservation and society from the SerengetiAnthony R.E. Sinclair
Centre for Biodiversity ResearchUniversity of British Columbia, Canada
Dr. Simon MdumaHead of TAWIRI & the SerengetiBiodiversity Progam
The Macaulay InstituteFrankfurt Zoological SocietyNSERC, CanadaNational Geographic SocietyWildlife Conservation Society
THANK YOU
THE TEAM
Simon MdumaStephen MakachaAlly NkwabiJohn MchettoAnne SinclairJohn FryxellRay HilbornRoy TurkingtonKris Metzgerand indirectly
Markus BornerSimon Thirgood and many others
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 behaves- lack of understanding could lead to surprise, inappropriate management, or even system collapse
THE WORLD PROBLEM
- therefore, one must understand important properties of ecosystems to apply
- effective management
- effective conservation
THE NEED
Changes in Ecosystems can lead to unexpected outcomes
Flathead Lake, Montana
Opossum shrimp added to provide extra food forKokanee Salmon Bald eagles
0
20
40
60
80
100
120
140
160
1978 1980 1982 1984 1986 1988 1990
Ab
un
dan
ce In
dex
Bald Eagles x 7
Kokanee x 1000
Opossum shrimp
Flathead lake, Montana
Spencer et al. 1991 BioScience
Unexpected events occur because ofcomplex interactions.
Illustrated by events in Serengeti, Tanzania
Rift
val
ley
Rift
val
ley
Isuria
Sca
rp
Ol DoinyoLengai
Meru4565
Ketumbaine2942
Gelai2962
Olduvai
gorge
The Serengeti Ecosystem
Salaiplains
Serengetiplains
Loitaplains
From Grant Hopcraft
KENYA
TANZANIA
SERENGETI IS COMPOSED OF TREELESS PLAINS
..AND SAVANNA WOODLANDS
Wildebeest is the dominant species
Wildebeest migration patterns
TANZANIA KENYA
40 0 40 80 Kilometers
Mean Annual Precipitation
Mean Annual Precipitation (cm)36 - 4646 - 5555 - 6464 - 7373 - 8383 - 9292 - 101101 - 111111 - 120No Data
SNP Boundary
Kris Metzger
The reasonfor dry season migration
1200
400
Serengeti Wildebeest Population outbreak – the event that changed everything – to understand it we must go back a century
0
300
600
900
1200
1500
1800
1950 1960 1970 1980 1990 2000
Po
pu
lati
on
Siz
e (x
100
0)
The Great RinderpestThe 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
Rinderpest
0
20
40
60
80
100
1955 1960 1965 1970
% w
ith A
ntib
odie
s
Years
Wildebeest
Buffalo
Incidence of Rinderpest in Serengeti
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 producesa distorted age structure of old trees
% Acacia tree canopy cover drops rapidly in the 1960s
05
1015202530
1940 1960 1980 2000
Year
% A
caci
a C
anop
y
H.Dublin 1986
Northern Serengeti, Mara triangle 1944
Photo Syd Downey
1983
Wildebeest grazing reduces grass fuel and area burnt
0
10
20
30
40
50
60
70
80
90
100
1960 1970 1980 1990 2000
% A
rea
Bu
rnt
SERENGETI AREA BURNT IN DRY SEASON
0
20
40
60
80
100
0 500 1000 1500
Wildebeest number (thousands)
% a
rea
bu
rnt
Increase in wildebeest causes decreasein burning
Complex interactions of wildebeest and the environment
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 1986
20031991
Savanna
Martin and Osa Johnson 1928
Osa Johnson filming from plane 1933
NYARABORO FROM EMAKAT
1928 1982
2003
-0.2
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
1920 1930 1940 1950 1960 1970 1980 1990 2000 2010
rate
of
chan
ge
in
tree
sSERENGETI TREE DENSITY
Instantaneous rate of change in tree density negative 1920s-1960s, then increases rapidly in 1980s, 1990s following wildebeest
Lions use thickets to capture prey
- more thicket improves success
Lions use thickets to capture prey
- more thicket improves success
0
50
100
150
200
250
300
350
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
Lio
n n
um
be
r
0
200
400
600
800
1000
1200
1400
1600lion
wildebeest
Serengeti woodland lion numbers Serengeti woodland lion numbers increase in the 1990sincrease in the 1990s
Wild
ebeest x 1000
Wild
ebeest x 1000
Lion data from C. PackerLion data from C. Packer
0
10,000
20,000
30,000
40,000
50,000
1970 1975 1980 1985 1990 1995 2000 2005
Imp
ala
nu
mb
er
0
2,000
4,000
6,000
8,000
10,000
12,000T
op
i nu
mb
er
impala
topi
Decrease in most resident prey
Disturbance and multiple statesDisturbance and multiple states
Ecosystems are continually being disturbed
weather eventshuman harvestinginvasions of speciespredation
Disturbance can cause a change of state
Disturbance changes ecosystems – which do notalways 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 predationTrees 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…..
0
500
1000
1500
2000
2500
3000
3500
1950 1960 1970 1980 1990 2000 2010
Nu
mb
er
SERENGETI ELEPHANT POACHING
IVORY BAN
..resulting in much food for elephants in the 1990s and 2000s inSerengeti but not the Mara (wildebeest in both)
KENYA
TANZANIA
SERENGETI - MARA 2005
-hence ecosystems can have more than one state under the same conditions
Tibetan yak
Tibetan grasslands near Naqu
0
2
4
6
8
10
12
0 2000 4000 6000 8000 10000
Livestock equivalents
Nu
mb
er o
f o
utb
reak
sMONGOLIA – Brandt’s vole outbreaks
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
0
10000
20000
30000
40000
50000
60000
70000
80000
Wahine Storm, 1968
Nu
mb
er o
f sw
ans
CHANGE IN STATE: swans on Lake Ellesmere, New Zealand
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 stabilityBiodiversity and stability
• species diversity and community resilience
e.g. Australian Eucalypt woodlands
Original closedeucalyptwoodland
Degraded eucalypt woodland
Drawings Frank Knight
Noisy miners reduce or exclude…..
…white-plumed honeyeaters and otherspecies in degraded Eucalypt woodland
Loss of bird diversity in Australian woodland
Psyllid outbreaks in isolated trees of farmland
Eucalypt dieback – eastern Australia
Psyllid insect outbreaks cause dieback in exposed trees-disruption of intact forest causes biodiversity loss and ecosystem disfunction
Long time scales - The effects of historyLong time scales - The effects of history
Disturbance events take a long timeTo 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
0
10000
20000
30000
40000
50000
60000
70000
80000
1890 1910 1930 1950 1970 1990 2010
Nu
mb
er
Observed
Reported
The GreatRinderpestepizootic
removed
Buffalo long-term change 1890-2003
Poaching
Data from Sinclair & Mduma
0
1
2
3
4
5
6
1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980
Lo
g F
req
uen
cyAcacia tree density 1880-1980
The great rinderpest
Disturbance and history
THE IVORYTRADE
1840s – 1890s
TIPPU TIPThe great slavetrader of easternAfrica
- 1860s to 1890s
Ivory from Zanzibar
0
50
100
150
200
250
300
350
1840 1850 1860 1870 1880 1890 1900kg
x 1
000
Ivory from Khartoum
0
50
100
150
200
250
1840 1860 1880 1900 1920
kg x
100
0
EAST AFRICAN IVORY EXPORTS
Data from C. Spinage 1973
0
500
1000
1500
2000
2500
3000
3500
1850 1900 1950 2000
Nu
mb
er
counts
reports
The Ivory trade
Poaching
SERENGETI ELEPHANT
CITESIvory ban
The effects of historyThe effects of history
Ivory hunting – affected the vegetation in Protected areas such as Tsavo (Kenya) andChobe (Botswana), and altered the long-termcourse of conservation in Africa.
It also decimated human populations and prevented human advancement
Disturbance and historyDisturbance 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
SAHEL
Traditional Human migrations in the Sahel follow rain
Boreholes have been sunk in the Sahel since the 1960s topresent. Sedentary life style has resulted in overgrazing
Photo A. de Vos 1975
.. and repeated famines. MALI FAMINE 1973
MALI –
TheGreen Polygon1973demonstratesovergrazingnot drought
The ranchboundary
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 messageConservation 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 toProtected Areas
- ecosystems are continually changing
Current protection strategy is not addressing this issue- we need to find a new way to accommodate change