Valuation of Ecosystem Services

Valuation of Ecosystem Services Author(s): Brian W. van Wilgen, Richard M. Cowling and Chris J. Burgers Source: BioScience, Vol. 46, No. 3 (Mar., 1996), pp. 184-189 Published by: Oxford University Press on behalf of the American Institute of Biological Sciences Stable URL: http://www.jstor.org/stable/1312739 Accessed: 24-08-2017 14:57 UTC REFERENCES Linked references are available on JSTOR for this article: http://www.jstor.org/stable/1312739?seq=1&cid=pdf-reference#references_tab_contents You may need to log in to JSTOR to access the linked references. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://about.jstor.org/terms

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Valuation of Ecosystem Services A case study from South African fynbos ecosystems

Brian W. van Wilgen, Richard M. Cowling, and Chris J. Burgers he term ecosystem services refers to the many conditions and processes associated with natural ecosystems that confer some benefit to humanity.

Examples include the generation and maintenance of fertile soils; preven-

tion of soil erosion; detoxification and recycling of waste products;

The delivery of water from catch-

ment areas, or watersheds, in the Watershed ecosystemsWestern Cape Province, South Afprovide quantifiable rica, serves as an example of a sig-

benefits that can

justify management

expenditure

regulation of the hydrological cycle

and of the gaseous composition of

the atmosphere; control of potential

agricultural pests; pollination; and for the explicit quantification, in preservation of the earth's genetic monetary terms, of the value of items library. formerly regarded as priceless. The Walter Westman's classic paper trend toward valuation persists to"How much are nature's services day. Yet few studies that we know worth?" (Westman 1977) raised the explicit ways of evaluatof present question of the value of conserving ing ecosystem services in order to ecosystems for the services they justify pro-the allocation of funds for vide to humanity. He pointed out maintenance and restoecosystem nearly two decades ago that Westration. This economic justification ern societies have increasingly is called important where strong competition exists for the public funding needed for conservation manage-

nificant contribution from natural

ecosystems to human well-being. The sustained supply of high-quality water depends on maintaining

the cover of fynbos (shrubland) veg-

etation (van Wilgen et al. 1990).

Fynbos vegetation is adapted to the summer droughts and nutrient-poor soils, as well as to the fires that occur periodically in the Cape moun-

tains. The fynbos binds the soil, preventing erosion, while its relatively low biomass ensures conservative water use and low-intensity

fires, which in turn ensure high wa-

ter yields and low impacts on the

soil from periodic fires. South Africa is a dry country, and water is a resource that is likely to limit growth (Huntley et al. 1989). Catchment management is compliBrian W. van Wilgen is an ecologist in ment. cated by the invasion of the fynbos the Division of Forest Science and Techby nonindigenous woody In this article, we present vegetation a case nology of CSIR, Jonkershoek FRC, trees and shrubs, which increase biostudy showing how invasion by alien Stellenbosch, 7599, South Africa. His mass and reduce runoff. The eradiplants has affected water resources research has focused on the effects and in the mountain catchment areas of cation of these weed species is seen use of fire in African ecosystems, espeby ecologists as a major part of the Western Cape Province, South cially Cape fynbos. Richard M. Cowlcatchment management (van Wilgen Africa. To provide an explicit acing is director of the Institute of Plant et al. 1990). Recent reviews have Conservation, Botany Department, thecounting of the monetary value of stressed that invasion of catchment University of Cape Town, Rondebosch,maintenance of the ecosystem, we 7700, South Africa. His main interestsevaluate the benefits associated with areas by alien trees and shrubs would

are in the conservation and use of the

a reliable supply of water (an eco-have serious effects on water supservice). We compare theplies (van Wilgen et al. 1992, Versfeld and van Wilgen 1986). costs of a program of eradication of

flora of the Cape Floristic Region. Chris system J. Burgers is an ecological planner with

Cape Nature Conservation, Stellenalien plants with these benefits andEcologists have recognized this probbosch, 7599, South Africa. His duties provide estimates of the costs oflem for many decades, but it has not include the development of plans for abandoning the program in the faceyet received significant attention the conservation and management of from policy makers. To justify fundof declining funding and competing Cape fynbos vegetation. ? 1996 Ameriing for the maintenance and restocan Institute of Biological Sciences.demands for public funds. BioScience Vol. 46 No. 3

184


ration of fynbos vegetation, it is

necessary to be explicit about actual costs and benefits in monetary terms.

The importance of fynbos watersheds The fynbos mountain watersheds are

home to a major part of the Cape flora. In terms of endemic plant biodiversity, the region has been recognized as the world's "hottest" hot spot (Myers 1990). The Cape flora constitutes one of six biogeographic subdivisions, termed plant

kingdoms, of the world. The Cape

flora comprises 8574 species of vas-

cular plants, 68.2% of which are endemic, and 989 genera of plants, 19.5% of which are endemic (Bond and Goldblatt 1984, Cowling et al. 1992). The mediterranean-type cli-

mate area of South Africa is charac-

terized by cool, wet winters and

warm, dry summers. Regular fires

are considered necessary for the

maintenance of the diversity of Cape

flora, because fire triggers impor-

tant phases of the life cycles of some

plant species, such as seed release

and germination. To rejuvenate the vegetation, prescribed burns are conducted at intervals of around 12-15

years in the late summer to early autumn period. The Cape, like other mediterranean-

type climate areas worldwide, is a focus of human immigration and population expansion, which makes

these areas-and their associated

ecosystems-disproportionately susceptible to potential environmental

stress and degradation (Di Castri 1994). Cape Town, the largest city

in the region, currently has a population of 2.2 million, which is proFigure 1. Pinus pinaster invading a fynbos mountain watershed. The increases in

jected to reach 3.5 million bybiomass the and structure are striking. Following several fire cycles, closed canopy year 2000 and 6.2 million by 2020stands can develop and completely replace the native fynbos. Photo: G. G.

an annual increase of between 4%

Forsyth.

and 5 %. The region's other city (Port

Elizabeth, 800 km to the east of Cape Town) is likely to experience Fynbos-clad mountain catchments similar growth, and even greater fulfill approximately two-thirds of growth is predicted for the rapidly the Western Cape's water require-

developing industrial areas at Mossel ments. This ecosystem service plays Bay (400 km east of Cape Town) a crucial role in the region's economy and Saldanha Bay (120 km north of and contributed a gross domestic Cape Town). In addition, the region product of US$15.3 billion in 1992

supports extensive irrigated crop- (Bridgeman et al. 1992). The conlands, producing deciduous fruit, tinued growth of the industries that

wine, and wheat for local consump- make up the Western Cape Province's tion and export. economy, which will be necessary to

support the growing population of the region, is limited by the availability of water. For example, the deciduous fruit industry is entirely dependent on water derived from adjoining mountain catchments; in 1993 this industry generated a gross

export earning of $560 million and provided employment for approximately 250,000 people. The Western Cape is also home to

March 1996

185


large and rapidly growing numbers of economically marginalized people who live in informal settlements on the periphery of urban centers. The

cies) among the Cape flora (CowlNorth America (Stirton 1978). ing and Hilton-Taylor 1994). In fynbos, alien woody weeds fall The unique and spectacularly into two broad groups. The most

beautiful fynbos flora is an internaimportant group includes serotinous

Reconstruction and Development Programme of South Africa's Gov-

tionally recognized ecotourist replants (plants with seeds stored in source (Bridgeman et al. 1992). cones or persistent fruits) such as Tourism in the region is substantial; Hakea sericea and Pinus pinaster, for example, approximately 400,000which are killed by fire and then

ernment of National Unity (African

National Congress 1994) endorses

the principle that all South Africans

release the seeds held in closed serotourists visit the Cape of Good Hope

have a right to "convenient access

Nature Reserve each year, an areatinal cones. To eliminate these

to clean water." Yet most of these of enormous plant biodiversity im-plants, they are felled before burnpoorer communities currently do not mediately south of Cape Town. A ing. The seeds of the alien plants are have access to reliable sources of major growth industry in the West-then released, after which they ei-

clean water. Optimal catchment ern Cape, ecotourism has great pother germinate or are consumed by management is necessary to ensuretential to provide employment and rodents. Approximately one year that this water is made available fuel economic growth in an eco-after felling, the area is burned and and delivered in the most cost-effecnomically and ecologically sustainthe seedlings of alien plants are tive manner possible. able way (McNeely 1988, Swanson killed. However, regular follow-up Although the sustained delivery 1991). Uncontrolled alien plant inweeding operations are required to eliminate the few individuals that of water alone should justify the vasions are a significant threat to

the ecotourism resources of the West-inevitably escape the fire. These folexpenditure of public funds on optimal catchment management, alien-ern Cape. low-up operations are usually carfree catchments provide a wide range ried out 2.5 and 10 years after burnof additional ecosystem services and ing (Macdonald et al. 1985). Alien plants in economic opportunities. The fynbos The second group of weeds in-

fynbos watersheds

flora is widely harvested for cut flow-

ers, dried flowers, and thatching Fynbos ecosystems are remarkably grass (van Wilgen et al. 1992). The prone to invasion by alien woody combined value for 1993 of these weeds (trees and shrubs; Figure 1). enterprises, much of which was made These weeds displace the native up of export earnings, was $18fynbos and increase biomass by be$19.5 million and provided a livelitween 50% and 1000% (Versfeld hood for 20,000-30,000 people and van Wilgen 1986), resulting in (Cowling and Richardson 1995). significant decreases in runoff from catchment areas. The weeds are also Many fynbos plants have been developed as food and drug products fire-adapted species, which compli(Donaldson and Scott 1994). Forecates the program of prescribed most amongst these is rooibos tea burning. Whereas weed-free areas (Aspalathus linearis), one of the 245 can easily be subjected to prescribed

cludes those species with continual seed release (e.g., Australian Aca-

cia species). Large quantities of hard-

coated seeds accumulate in the soil

(Richardson et al. 1992). In this case, control is more problematic.

Felling and burning results in abun-

dant seedlings, which need to be cleared by hand-pulling-a time-

consuming and labor-intensive process.

Invasion of fynbos watershed eas by alien plants results in ch to vegetation structure that fu mentally alter the nature of th

species of this genus in the Cape burns, areas infested by weeds first flora. The rapidly growing exports have to be cleared if their spread of this tea generated foreign exafter fire is to be prevented. Therechange of $2.1 million in 1993. Refore, an active program aimed at the

creases in fuel loads and therefor

velop species of Cyclopia, an

fire intensity. Access to affect eas becomes difficult, and the

eradication of alien trees and shrubs search is currently underway to de-

is carried out in catchment areas

endemic fynbos genus in the Faba- (van Wilgen et al. 1990).

ceae, as a high-quality health tea.

management problem. Increa aboveground biomass result i

struction and maintenance of fire

The invasive plants were introbreaks becomes onerous, expensive, Several other plants, including hor- duced to South Africa to provide a largely ineffective. These and

ticultural and medicinal crops, source of fast-growing timber in changes the are difficult to quantify in are currently used commercially;relatively treeless landscape and also monetary terms. In some areas, how-

undoubtedly many as yet undiscov- as hedge plants, as agents for bindever, these changes have led to the ered plants would provide similaring shifting dunes along the coast, deterioration of the ecological inopportunities. and as ornamental plants. The tegrity inof watersheds to the point Many of these services are based troductions began with European that they become a financial burden on the phenomenal biodiversity ofsettlement of the area in the midrather than an asset. For example, fynbos ecosystems. Alien plants are seventeenth century and gained on the slopes of Table Mountain, recognized as the greatest threat to momentum in the early nineteenthabove the city of Cape Town, invathis biodiversity (Richardson et al.century. Not all introduced plants sion by alien plants has increased 1992) and are largely responsible have become invasive. The most fire intensities, leading to severe soil for the extraordinarily high numberimportant invasive species originated erosion (Scott and van Wyk 1990, of endangered and threatened taxa in Australia and the mediterraneanScott et al. 1991). At the same time, (1406, or 16.4% of all plant spetype climate areas of Europe andthe elimination of indigenous plants 186

BioScience Vol. 46 No. 3


600

E E

the results from watershed experi-

- . ~ ments in the Cape mountains as a basis. These experimental water/.-- sheds, many of which have continu-

500

r

0o

o

0

400

-/. ^ous records of streamflow and rain-

300

- ~ ^~fall covering more than a half a

200

300

260

c:

_/^~~ ^century, have clearly shown that 1500 afforestation with alien plants can 5000 1000 150o0 200 decrease streamflow (van Wyk

-

CD

E

100

20I-

180 140 *

n

Biomass (g/m2) 1987). In the experimental water-

0

20

Figure 2. Relationship between biomass sheds, the biomass of natural and

.

t^

'I

I

vi

\

\

40

60

80

100

Time

luction in streamflow from nine alien vegetation had been detergauged catchments in the Western Cape mined, and the growth rates of Figure and rec

with va

from

This re reducti catchm

(solid

rying degrees of invasion by alien invasive plants and natural vegetatrees (f rom Le Maitre et al. in press). tion between fires were known.

lationship was used to simulate The model, which runs on a geo-

ons in streamflow in invaded graphic information system is initi-

~ents"~~. ~ated with a known mixture of natural vegetation and alien plants. It

has furrther favored erosion through assumes an interval of 15 years bea redu( ced capacity to cover and pro- tween fires (the mean return intertect th e soil after fires. As a result, val calculated from fire records). enorm

ous sums of money have had After each fire, the aboveground

Cape

3. the

In

line)

line

years

(f

their

(in

S K

Prov

(dashed

15

(yrs)

s

press)

Kogelberg Cape Tow of alien p

to be pent s after each fire to remove biomass of the area is assumed to be sedime nt from the city's stormwater reduced to zero; alien plants increasesimulations were initiated. The drains.,roads, and houses. Similar in density and also spread to adja- model indicated that alien

plants proble ms could develop elsewhere cent areas (these simulations were would invade approximately 40% in the region as the population en- based on known rates of prolifera-of the area within 50 years and 80% croach es on mountain areas. tion and spread for the species conafter 100 years, with a correspond Cur rently, funding for watershed cerned). The biomass of the water- ing increase in biomass of 150% o manag ement in South Africa is un- shed between fires was simulated

more. This invasion would result in an

der pr essure, especially in view of using the known rates of growth average decrease of 347 m3 * ha-' yr-1 of for the co] mpetition for funds from so- both alien plants and nativewater vegetaover 100 years, resulting in cial pi rojects in the postapartheid tion. Because of the higher average growth losses of more than 30% of era. T he new democratic govern- rates of alien plants, the biomass the waterof supply to the city of Cape ment is s not likely to allocate enough watersheds increased in theTown. simulaIn individual years, when fundin g to catchment management tions as the watersheds became large areas in- would be covered by unless mature trees, losses would be much the expenditure of public vaded. funds can be justified in terms of the Le Maitre and his coworkers greater, (in exceeding 50% of the runoff from betterr nent of human well-being. The press) established a statistically sig-similar uninvaded areas South African situation is not nificant relationship between (Figure above3).

unique . Governments elsewhere, es- ground biomass and reductions in

peciall y in the developing world, streamflow, based on the long-term Economics of water and emselves in similar situations, watershed experiments described catchment management ch the conservation and main- above (Figure 2). Although the exWe examined the economics of watenanc e of ecosystems is difficult to act mechanisms of the reductions andare catchment management in they justify in the absence of a sound are not clearly understood,ter econor nic evaluation. Such evalua- undoubtedly a function of two ways. both in-First, we compared the tions a ire difficult to find, but they creased transpiration and intercepcosts of developing water supply includi e the Amazonian rain forests, tion of rainfall by alien trees. facilities (dams and water distribuBoth where tion networks) in two identical exploitation of nonwood re- of these variables are increased by source s would provide profits while increases in the leaf area as catchments, with and without the the vegconser ving the forests (Peters et al. etation becomes dominated by tall of alien weed populamanagement

find th in whic

1989).

alien trees instead of short shrubs; tions. Second, we compared the costeffectiveness of optimal catchment these increases are easily described

Thempacts ii of alien plants on using biomass, a surrogatemanagement measure to alternative means of securing water supplies, such as resources of leaf area. recycling The relationship between simu-or desalinization of seawater. Le Ma itre et al. (in press) have de- lated biomass and streamflow reThe assumptions made for t velope d a model to simulate the ef- ductions was used to calculate the fects o n water yield of invasion of water yield between fires, using sce-identical catchments (Tab two were derived from established relawaters ;heds by alien plants, using narios with and without alien plants. water

187

March 1996


tionships between rainfall, runoff,

and the aboveground biomass of

vegetation, as modeled by Le Maitre

et al. (in press). A 10,000-hectare

catchment, with 1500 mm of rainfall annually, would support around 3800 g/m2 of fynbos vegetation at

15 years postfire. The same catch-

ment, if fully invaded by alien trees

and shrubs, would support a bio-

mass of around 11,000 g/m2 at the

same stage. The catchment would yield 742 mm (rainfall equivalent) of streamflow under conditions of

Table 1. Assumptions for parameters, together with costs and water yields, in two

identical catchments, with and without the management of alien weed populations. Vegetation classes are from Le Maitre et al. (in press). Biomass and

streamflow reductions were calculated from relationships given in Le Maitre et al. (in press). With the management Without the management Catchment descriptor of alien plants of alien plants Area (ha)

10,000

10,000

1500 Mean annual rainfall (mm)

Postfire age (years)

15

70% short ericoid-restioid

Vegetation cover

fynbos; 30% tall moist

no aboveground vegetation (as found immediately after fire), or

fynbos

74.2 x 106 m3/yr. Capital cost of clearing The costs of management of alieninitial infestations plants can be divided into the clear-($/ha) ing of existing stands of alien plants Capital cost of developing

and the subsequent follow-up op-water supply facility erations required to keep these ar-(millions of $)

eas free of new invaders. The costs

Capital cost of building wate of initial clearing amount to besupply facility plus initial tween $140 and $830 per hectare, clearing of aliens depending on the density of inva(millions of $) sion; annual follow-up operations

Annual interest on capital are estimated to cost $8 per hectare cost at 8% (millions of $) over large watershed areas.

A report on the potential water Cost of alien plant managemen

830

1500 15

33% tall alien shrubs; 33% medium alien trees;

33% tall alien trees 0

67.7

67.7

76

67.7

6.1

5.4

8

0

supply facilities in the Western Cape (an operating cost, $ ? ha1 - yr-' (DWAF 1994) lists 20 remaining sites Operating cost of water for the development of water supply supply facility facilities in the province. The capi-(millions of $ per year) tal costs of building these facilities

1.29

1.29

1.37

1.29

7.47

6.69

Total operating costs range from $0.83-$215 million,

(alien plants plus water with a mean of $1.08 per cubic meter supply facility; millions of water. We used this mean to estiof $ per year)

mate the cost of a theoretical water

supply scheme from a 10,000-hect-Total

annual costs

x 106(interest plus operating, meanmillions of $ per year)

are catchment yielding 62.7 m3/yr at $67.7 million. The operating costs amount to 2.1? per Aboveground cubic meter, or $1.29 million per(g/m2)

biomass

year for a 10,000-hectare catchment

Streamflow from catchment

(Table 1).

3867

10,964

742

742

114

256

The unit cost of water for the two without vegetation (mm rainfall equivalent)

hypothetical catchments can be cal-

Reduction in streamflow culated by assuming an annual indue to plant biomass terest cost on capital outlays (the

15 years postfire building of a water supply facility in

at

(mm rainfall equivalent)

both cases, and the initial clearing

of alien plants in one) and combin- Water ing this cost with the annual operat-

ing costs (Table 1). We used 8%

yield (x 106 m3/yr)

Unit cost of water (e/m3)

62.7

48.6

11.9

13.8

inflation as a conservative estimate, because inflation in South Africa

duction is 14% lower because of the would yield an additional 14.1 x over the past ten years has ranged 106 m3/yr of water, almost 30% between 10% and 16%. Although larger volumes of water that would more water than an unmanaged total annual costs are 11% higher be produced from a watershed where for the case in which alien trees are catchment. This last point is paralien trees are cleared and managed. Furthermore, such a watershed ticularly important in view of the managed, the unit cost of water pro-

BioScience Vol. 46 No. 3

188


limited opportunities for establishing new water supply facilities.

The alternatives to obtaining water from optimally managed

sions makes sound economic sense.

century. Cape Town (South Africa): Hu-

This practice would also restore and

man and Rosseau.

Le Maitre DC, van Wilgen BW, Chapman RA,

sustain biodiversity in catchment McKelly

areas and thus enable the mainte-

D. In press. Invasive plants and

water resources in the Western Cape Prov-

catchments are not attractive. A sew-

nance and growth of economic en-ince, South Africa: age effluent exchange plant that terprises based on fynbos plants. quences of a lack of of Applied Ecology.

would deliver the same volume of

modelling the consemanagement. Journal

The challenge we and other Western Macdonald IAW, Jarman ML, Beeston P. 1985. water as a well-managed catchment Cape scientists face is to convinceManagement of invasive alien plants in the

of 10,000 ha (62.7 x 106 m3/yr) policy makers of the wisdom, forfynbos

would cost $135 million to build

biome. South African National Sci-

the long term, of allocating publicentific Programmes Report 111. Pretoria and would operate at $2.6 million funds for the optimal management (South Africa): CSIR. McNeely JA. 1988. Economics and biological per year. Using the assumption of of fynbos catchments. Doubtless,diversity: developing and using economic 8% interest on capital outlay, this many other scientists in many otherincentives to conserve biological resources. Gland (Switzerland): International Union example equates to a unit cost of nations face similar challenges. for the Conservation of Nature. $0.21/m3. Direct reuse of sewage Myers N. 1990. The biodiversity challenge: would cost $0.25/m3, whereas deAcknowledgments salinization would deliver water at

$0.80/m3. Thus these alternatives would deliver water at a cost between 1.8 and 6.7 times more than

expended hot-spots analysis. The Environ-

mentalist 10: 243-255.

Van Wilgen acknowledges CSIR and Peters CM, Gentry AH, Mendelson RO. the South African Department ofValuation of an Amazonian rain forest.

Environment Affairs and Tourism

1989.

Nature 339: 655-656.

Richardson DM, Macdonald IAW, Holmes optimal catchment management. for supporting this work. Cowling Cowling RM. 1992. Pages 271-308 in acknowledges the Pew CharitablePM, Cowling RM, ed. Plant and animal invaTrust for financial support. Conclusions sions: the ecology of fynbos-nutrients, fire

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