Transcript 1091-Lec27(Victoria)

Climate clarification
Albedo
Definition: the extent to which an object reflects
light from the sun
Range of values: 0 to 1
Impact: high albedo, high reflectance
less solar energy absorbed by object
Typical albedo
Snow
Tundra shrubs
0.8-0.9
0.2 summer
0.6 snow covered
Amazon forest
Amazon ranchland
0.13
0.18
Boreal forest
Boreal grass
0.08
0.2
Feedback loops
Warming will melt sea ice and promote growth of
shrubs in the arctic
Puddles and shrubs have lower albedo
(reflectance) than ice and tundra
Puddles and shrubs will warm up rather than
reflect solar energy
Warm puddles and shrubs will increase ice melt
and promote further shrubification
Feedback effects on climate
Impact of Deforestation
Ranchland has higher albedo
0.18 vs 0.13
 Surface absorbs less energy
 Cooling effect
Ranchland has much less evaporation
Warming effect
Net effect
WARMING
+- indicates effect of forest
on temperature
Feedback effects on climate
Impact of Deforestation
Grassland has higher albedo
0.20 vs 0.08
Surface absorbs less energy
Cooling effect
Grassland has slightly less
evaporation
Warming effect
+- indicates effect of forest
on temperature
Net effect
?????
Humans, fisheries and tough
conservation decisions
A Case study:
Lake Victoria’s Nile
perch fishery and
cichlid biodiversity
Lake Victoria
•
Largest lake in Africa (68,800
km2), seventh in the world by
volume.
•
Tanzania, Uganda and Kenya all
share the lake and its resources,
but regulations governing
resources are different in each
country.
•
Annual catch: 400-500,000 tons
bringing in US$250,000-500,000.
•
2 million people depend directly or
indirectly on fishing activities.
European History
1858 “discovered” by John Speke
- sparsely populated region
- subsistence fishery (small native species)
1902 – colonial government links lake to Mombasa
1930 – Europeans had deforested watershed
- planted tea coffee sugar tobacco cotton
- population had exploded
- urban centres provided market for fish
1950 – native tilapia commercially extinct
1951 - English introduce non-native tilapia
1955 – English introduce Nile Perch
Fishing history – the early days
Ngege
Catfish
Haplochromines
Impacts of Nile perch
1955 – introduced to Lake Victoria
1969-70 Haplochromines
Nile perch
1980’s
Nile Perch
Haplochromines
83% biomass
0.05%
80% biomass
<1%
Massive loss diversity
400+  200 species
Fishing history
– the next 30 years
Decline
has
continued
Lake Victoria – summary so far
•
The local multi-species fishery is
now dominated by 3 species and
supplies an international market
•
200 endemic Cichlid species were
driven to extinction in 30 years
•
Overfishing, industrial and
agricultural pollution, an increasing
human population and noxious water
weeds, all threaten the sustainability
of Lake Victoria.
•
The Nile Perch is being overfished.
What happened next?
Intensive fishing led to a resurgence of native
species
Haplochromine cichlids, particularly pelagic
species recovered
Three areas acted as refugia
- Wetlands and rocky habitats
- Hypoxic areas
- Satellite lakes
The future?
But current environment
is very different
New fauna will differ in
richness,
composition and
ecosystem function
The sociopolitical context
Award winning documentary by
Hubert Sauper is a tale about
Lake Victoria, humans in the
north and south, globalization,
corporate corruptness, and
fish.
The following are excerpts
from the film.
If goal is to conserve the remaining cichlid
diversity what should conservation
biologists do?
Options?
‘The Roundtable’
The Lake Victoria Fisheries Research project has organised fisheries managers to
work on quantifying the fisheries stocks of Lake Victoria and has also managed to
bring together scientists from the 3 countries to exchange views and identify gaps
in research and recommend how to deal with those gaps.
Planning for the lake’s future (economically and biologically) may proceed with a
two-pronged approach:
1. Managing the fisheries to maintain
the greatly increased yields and;
“The fisheries managers”
2. Conservation of the remaining
indigenous species.
“The conservation biologists”
Lake Victoria Fisheries Organization (LVFO) comprises
stakeholders whose objective is to
“protect and restore the lake”.
Where is the political power?
Whose interests are being protected?
Given the population pressure and the industry/political
pressure
what would YOUR conservation strategy be?
Possible avenues for biodiversity conservation
Conservation of habitat and biodiversity will only succeed if
water quality is improved –
nutrient levels and toxic contamination should be controlled
Stock management strategies linked to rational regulation of
fishing effort are needed
Representative habitats in the lake should be conserved with
focus on high diversity areas, refugia, satellite lakes and
shoreline wetlands
Development of an integrated basin wide plan
- international cooperation is necessary to regulate nutrient
influx and fishing pressure