The economic consequences of the environmental impacts of alien plant invasions in South Africa

Transcription

1 The economic consequences of the environmental impacts of alien plant invasions in South Africa David Le Maitre, Willem de Lange, David Richardson, Russell Wise and Brian van Wilgen

2 Outline Introduction Ecosystem service impacts Service valuation Impacts on service values Summary

3 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

4 Distribution of invasions

5 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

6 Impacts on surface & groundwater Volume of current runoff reduction (millions of m3) Volume of potential runoff reduction (millions of m3) Current reduction in annual groundwater recharge (thousands of m3) Potential reduction in annual groundwater recharge (thousands of m3) Fynbos shrublands Grassland Succulent karoo Nama karoo Savanna and thicket

7 Impacts on livestock grazing 6,000,000 5,000,000 Estimated potential number of large stock units Current potential with aliens 4,000,000 Future potential with aliens 3,000,000 2,000,000 1,000,000 0 Fynbos shrublands Grassland Succulent karoo Nama karoo Savanna and thicket

8 Biodiversity loss 100 Without alien plants With current levels of invasion With future levels of invasion Biodiversity Intactness Index (%) Fynbos shrublands Grassland Succulent karoo Nama karoo Savanna & Thicket

9 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

10 Basis for estimates of value Unit price of water Un-serviced R0.14/m 3 ; serviced R5.40/m 3 Mean R1.89/m 3 Livestock R2 471 per large stock unit Loss of biodiversity: intact R1 021/ha (fynbos) to R33/ha (Nama & Succulent Karoo)

11 Impacts on service values

12 Value of water services 120,000 Pristine Current levels of invasion Future levels of invasion Annual value (R millions) 100,000 80,000 60,000 40,000 20,000 0 Fynbos Grassland Succulent Karoo Water Nama Karoo Savanna and Thicket Total

13 Value of grazing services 40,000 Pristine Current levels of invasion Future levels of invasion 35,000 Annual value (R millions) 30,000 25,000 20,000 15,000 10,000 5,000 0 Fynbos Grassland Succulent Karoo Nama Karoo Savanna and Thicket Total Grazing

14 Value of biodiversity 25,000 Pristine Current levels of invasion Future levels of invasion Annual value (R millions) 20,000 15,000 10,000 5,000 0 Fynbos Grassland Succulent Karoo Nama Karoo Savanna and Thicket Total Biodiversity

15 Total value 160, ,000 Annual Value (R millions) 120, ,000 80,000 60,000 40,000 20,000 0 Pristine Current levels of invasion Future levels of invasion

16 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

17 Invasions and water resources

18 Aliens and grazing

19 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?

20 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

21

22 What has been done? Working for Water and partners Conventional control: /9 R4927 million ± people employed annually ± ha new clearing, ± ha followedup Partners: Provinces Forestry Industry

23 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