Post on 19-Aug-2018
transcript
The economic consequences of the
environmental impacts of alien plant invasions
in South AfricaDavid Le Maitre, Willem de Lange, David Richardson, Russell Wise
and Brian van Wilgen
Outline
Introduction Ecosystem service impacts Service valuation Impacts on service values Summary
Introduction
About 9000 plant species introduced, >200 introduced species have become
invaders in South Africa By 1996 ± 1.74 million ha (condensed)
invaded By 2007 ± 1.83 million ha (condensed) Largely woody, shrub and tree species
Distribution of invasions
Ecosystem service impacts Alter ecosystem structure & function affecting
Regulatory & supporting services Primary production ↑ Water, carbon & nutrient fluxes ↑ Fire regimes ∆ Soil stabilisation ↓ Disease regulation ↓
Production services: Surface & groundwater yields ↓ Natural rangeland productivity ↓ Other harvestable natural resources ?
Cultural services Science & education ? Tourism ?
Options ↓
Impacts on surface & groundwater
0
5000
10000
15000
20000
25000
30000
35000
40000
Fynbos shrublands Grassland Succulent karoo Nama karoo Savanna and thicket
Volume of current runoff reduction (millions ofm3)
Volume of potential runoff reduction (millions ofm3)
Current reduction in annual groundwaterrecharge (thousands of m3)
Potential reduction in annual groundwaterrecharge (thousands of m3)
Impacts on livestock grazing
0
1,000,000
2,000,000
3,000,000
4,000,000
5,000,000
6,000,000
Fynbos shrublands Grassland Succulent karoo Nama karoo Savanna and thicket
Estimated potential numberof large stock units
Current potential with aliens
Future potential with aliens
Biodiversity loss
0
10
20
30
40
50
60
70
80
90
100
Fynbosshrublands
Grassland Succulent karoo Nama karoo Savanna &Thicket
Bio
dive
rsity
Inta
ctne
ss In
dex
(%)
Without alien plants With current levels of invasion With future levels of invasion
Economic valuation
Economic assessments of plant invasions involve Valuation of both market and nonmarket
impacts Evaluation of trade-offs and risks
Many impacts are hard to value (especially public goods [commons])
Long-term thinking required Conflicts of interest
Basis for estimates of value
Unit price of water Un-serviced R0.14/m3; serviced R5.40/m3
Mean R1.89/m3
Livestock R2 471 per large stock unit Loss of biodiversity: intact R1 021/ha
(fynbos) to R33/ha (Nama & Succulent Karoo)
Impacts on service values
Value of water services
0
20,000
40,000
60,000
80,000
100,000
120,000
Fynbos Grassland SucculentKaroo
Nama Karoo Savanna andThicket
Total
Water
Ann
ual v
alue
(R m
illio
ns)
Pristine Current levels of invasion Future levels of invasion
Value of grazing services
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
Fynbos Grassland SucculentKaroo
Nama Karoo Savanna andThicket
Total
Grazing
Ann
ual v
alue
(R m
illio
ns)
Pristine Current levels of invasion Future levels of invasion
Value of biodiversity
0
5,000
10,000
15,000
20,000
25,000
Fynbos Grassland SucculentKaroo
Nama Karoo Savanna andThicket
Total
Biodiversity
Ann
ual v
alue
(R m
illio
ns)
Pristine Current levels of invasion Future levels of invasion
Total value
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
160,000
Pristine Current levels of invasion Future levels of invasion
Ann
ual V
alue
(R m
illio
ns)
Economic impacts
Annual losses currently: Water R5 798 million Grazing R338 million Biodiversity R428 million Total R6 564 million (±2.5 of 2009 GDP)
Australian wattles: 78-96% of impact
Invasions and water resources
Aliens and grazing
Summary
The environmental and socio-economic impacts are significant
They are increasing, rapidly in many areas They are unevenly distributed Yet they are often overlooked How do we change this?
Ecosystem services from this? Or this?
Thank you, especially to Working for Water for funding the research behind this presentation and to many colleagues for their contributions
What has been done?
Working for Water and partners Conventional control: 1995-2008/9 R4927
million ±22 800 people employed annually ±157 000 ha new clearing, ±420 800 ha followed-
up Partners:
Provinces Forestry Industry
Benefits of biological control
Biological control - savings through reduced invasions: R 8.3 billion from potentially invaded areas
R2.6 billion for water & R 1.1 billion grazing (grasslands)
R1.6 billion for biodiversity protection in fynbos Reduction in invasive succulents R2.9 billion