Linking Freshwater Flows and Ecosystem Services Appropriated by

ECOSYSTEMS
Ecosystems (1999) 2: 351–366
r 1999 Springer-Verlag
Linking Freshwater Flows
and Ecosystem Services
Appropriated by People: The Case
of the Baltic Sea Drainage Basin
ÅÅsa Jansson,1,2 Carl Folke,1,2* Johan Rockström,1,3 and Line Gordon,1
1Natural
2The
Resources Management, Department of Systems Ecology, Stockholm University, S-10691 Stockholm, Sweden;
Beijer International Institute of Ecological Economics, The Royal Swedish Academy of Sciences, Box 50005,
S-104 05, Stockholm, Sweden; 3RELMA, PO Box 63403, Nairobi, Kenya
ABSTRACT
Humanity’s dependence on ecosystem support is
‘‘mentally hidden’’ to large segments of society; it
has no price in the market and is seldom accounted
for in decision making. Similarly, the needs of
ecosystems for fresh water for generation of nature’s
services are largely invisible. Freshwater assessments predominantly have focused on human uses
of liquid water in rivers, lakes, and reservoirs. We
estimated the spatial appropriation of terrestrial and
marine ecosystems—the ecological footprint—of the
85 million inhabitants in the Baltic Sea drainage
basin with regard to consumption of food and
timber and waste assimilation of nutrients and
carbon dioxide. We also estimated the amount of
fresh water—the water vapor flow—that the inhabitants depend upon for their appropriation of these
ecosystem services. The ecological footprint estimate corresponds to an area as large as 8.5–9.5
times the Baltic Sea and its drainage basin with a per
capita ecosystem appropriation of 220,000–250,000
m2. This large estimate is mainly attributed to
carbon sequestering by marine ecosystems and forests. The water vapor flow of the ecological footprint
of forests, wetlands, agriculture, and inland water
bodies for making the human appropriation of
ecosystem services possible is estimated at 1175–
2875 km3 y⫺1. Human dependence on water vapor
flows for ecosystem services is as great as 54 times
the amount of freshwater runoff that is assessed and
managed in society. Decision making on an increasingly human-dominated planet will have to address
explicitly the critical interdependencies between
freshwater flows and the capacity of ecosystems to
generate services. We advocate a dynamic ecohydrological landscape-management approach upstream and
downstream in watersheds to reduce unintentional
impacts, irreversible change, and further loss of freshwater resources, ecosystem services, and resilience.
INTRODUCTION
others 1994). The human dimension on earth has
expanded to such an extent that all ecosystems are
modified by human activities (Boulding 1966; Daly
and Cobb 1989; Vitousek and others 1997). The
pervasive worldwide alteration of terrestrial and
aquatic habitats by an expanding human popula-
Key words: ecosystem services; ecological footprints; life-support systems; freshwater management; watershed; Baltic Sea drainage basin.
Human societies depend on life-support systems for
welfare and survival (Odum 1989; AM Jansson and
Received 6 October 1998; accepted 30 March 1999.
*Corresponding author; e-mail: calle@system.ecology.su.se
351
352
Å. Jansson and others
tion may lead to a drastic reduction in ecosystem
services per capita (Cairns and Pratt 1995).
The Sustainable Biosphere Initiative (SBI) (Lubchenco and others 1991) was a call for action to
ecologists to become more active in contributing to
ecological understanding for decision makers and
thus for improved management of the combined
human–nature system. In a comment to the SBI,
Grubb and May (1993) challenged ecologists ‘‘to
provide estimates of carrying capacity for human
populations in all main landscape types of the
world, using various assumptions about the standard of living to be enjoyed.’’ In this article, we
accept this challenge, recognizing that ecosystems
are complex self-organizing systems with nonlinear,
multiple-stable states and threshold effects (Carpenter and Leavitt 1991; Holling and others 1996). We
begin by estimating the area of forests, agricultural
land, wetlands, inland water bodies, and marine
systems that are appropriated by people living within
the Baltic Sea drainage basin (BDB) to satisfy their
present use of ecosystem services. Here, ecosystem
services refer both to biomass production, such as
trees and crops, and processes, such as pollination,
nutrient assimilation, and carbon sequestering. They
are all the result of nature’s work (de Groot 1992;
Baskin 1997; Daily 1997).
Fresh water is critical for industrial society (Gleick
1993; Postel and others 1996). Fresh water is also
critical for the ability of ecosystems to generate and
sustain services to society (Baskin 1997; Folke and
Falkenmark 1998). We link fresh water to ecosystems by estimating the amount of freshwater flow
that people in the BDB indirectly need for their
appropriation of ecosystem areas for ecosystem
services. This societal dependence on ecosystem
freshwater flows is largely ignored in the usual
models of water, resource, and environmental management.
The article is divided into three major sections. In
the first section, we estimate the appropriated ecosystem area, or ‘‘the ecological footprint’’ (Folke and
Kautsky 1989; Rees and Wackernagel 1994), of
people living within the BDB. We (a) analyze the
area of agricultural land, forests, and marine systems required to provide the population with wood,
paper, fiber, and food products, including seafood;
(b) analyze the area of agricultural land, forests,
lakes, and wetlands needed to sequester CO2 emissions and assimilate excretory release of nitrogen
(N) and phosphorus (P) from the population in the
basin; and (c) present an estimate of the aggregated
appropriation of terrestrial and aquatic ecosystems
by the entire human population in the BDB, taking
into account the issue of joint products of ecosys-
tems (for example, Costanza and Hannon 1989) to
avoid double counting.
In the second section of the article, we present
our analysis of freshwater flows for ecosystem services in the BDB. We estimate the appropriation of
renewable fresh water in industrial and domestic
activities, in the form of runoff, which we refer to as
‘‘liquid water appropriation’’ by humans. But we
also estimate the renewable freshwater requirements, measured as evapotranspiration, of the ecological footprints arrived at in the first section. The
footprints for the generation of ecosystem services
include forests, agriculture, wetlands, and lakes. We
call this indirect freshwater use by the human
population ‘‘water vapor dependence.’’
In the last section, we discuss our results and their
implications in relation to availability of freshwater
flow and ecosystem support in the region and
elsewhere. We conclude that in a world of pervasive
human dominance it is necessary to radically improve the management of links between fresh water, human activities, and ecosystem support. An
ecohydrological landscape perspective that treats
scarce fresh water and ecosystem services as interdependent may contribute to such an improvement.
ECOSYSTEM APPROPRIATION BY PEOPLE
IN THE BALTIC SEA DRAINAGE BASIN
The Baltic area is a large region with a drainage
basin of 1.7 million km2 and a brackish sea of
415,000 km2. The drainage basin includes 14 countries (Figure 1) with a total of approximately 85
million people, with varying standards of living
among the countries. Land use in the basin is
presented in Table 1. The region is in social and
economic transformation, particularly in the Eastern European countries. Although this development recognizes environmental issues, it does not
take into account the region’s dependence on ecosystem life support. Here we illustrate this dependence
by estimating terrestrial and aquatic ecosystem areas appropriated by the 85 million people in the
BDB for their use of some ecosystem services.
Methods
Ecosystem areas appropriated for renewable resource
production. We estimated the agricultural (cropland and pasture), forest, and marine ecosystem
areas required to produce the wood, paper, fiber,
and food products, including seafood, consumed by
the human population in the BDB. Data on appropriated area per capita in the different countries
were obtained from a study on the renewable
resource appropriation by cities in the BDB, based
Freshwater, Ecological Footprints, and Ecosystem Services
Figure 1. The Baltic Sea drainage basin.
Table 1. Land Cover and Sea Surface in
the Baltic Sea Drainage Basin
Ecosystem Type
Area in BDB
(km2 ⫻ 103 )
Forest
Agricultural land
Wetland
Inland waterbodies
Other land use
The Baltic Seaa
836
457
138
107
207
415
Source Sweitzer and others (1996).
aSource Stålnacke (1996).
on existing national data (Folke and others 1996).
This study did not include Belarussia and Norway.
Per capita appropriated forest, agricultural, and
marine areas in Belarussia and forest and agricultural land in Norway were calculated in the same
fashion as for the other countries (Folke and others
1996). Per capita appropriated marine area in Norway was based on Swedish data.
Data on food and fiber consumption and land-use
statistics were obtained from the FAO computerized
353
database Agrostat. We consistently used supply, as
defined by FAO, as a measure of total consumption,
rather than direct or actual per capita consumption.
The use of supply is preferable to consumption
because supply also includes losses incurred on
storage, transport, processing, etc. The FAO-catch
data used in our estimates do not include discards,
which may be as much as a third of recorded fish
catches (Pauly and Christensen 1995).
Population data and land use in the region were
obtained from Sweitzer and others (1996), data on
shelf areas and marine exclusive economic zones
from the World Resources Institute on Diskette
Database (1992), and fish yields from North Sea
data. For a detailed presentation of the methodology and statistical sources behind the estimates, see
Folke and others (1996).
Ecosystem areas appropriated for waste assimilation.
Waste emission to air, land, and water is a serious
problem in most parts of the BDB. Waste assimilation is a major ecosystem service. In this article, we
focus on ecosystem assimilation of carbon dioxide
(CO2 ), nitrogen (N), and phosphorous (P). We
estimate the area of forests, agricultural land (cropland and pasture), inland water bodies [lakes, reservoirs, and major rivers; see Sweitzer and others
(1996) for more detail], natural wetlands (bogs and
fens), and marine ecosystems that would have to be
appropriated by the human population in the BDB
for processing of their CO2, N, and P emissions. The
ecological footprint analysis of nutrient assimilation
only includes the excretory release by humans of P
in sewage sludge and N in processed water from
sewage treatment plants. Consequently, it is an
underestimate, because N and P emissions from
food processing, household waste, car emissions,
and other sources are not included in the analysis.
Background data for part of the analysis were
derived from Folke and others (1997).
Terrestrial ecosystems, especially forests, play an
important role in the earth’s carbon cycle. Forests
have high rates of primary productivity, and thereby
of carbon sequestering (Winjum and others 1992).
At present, largely due to tropical deforestation,
only mid- and high-latitude forests are net carbon
sinks (Dixon and others 1994). The average annual
net carbon sequestering rate of forests in the BDB
has been estimated at 30–60 metric ton C per km2
(Folke and others 1997). Other net CO2 sinks in the
BDB are natural peat producing wetlands and inland water bodies. Natural peat producing wetlands
have an annual carbon assimilation rate of approximately 8–55 metric ton C km⫺2, and the annual
carbon storage potential in lake sediments has been
estimated at 10–51 metric ton C km⫺2 (Eriksson
354
Å. Jansson and others
1991). The inland water bodies and wetland areas
correspond to approximately 25% of the region’s
forested area. We assumed that natural peat producing wetlands and inland water bodies sequester
carbon at maximum capacity to avoid overestimating the appropriated forest area. IPCC (Houghton
and others 1996) reports that oceans absorb between 20% and 57% of the carbon from annual
global CO2 emissions from fossil fuel combustion.
The Baltic Sea is not a net sink of CO2 emissions (F.
Wulff, Stockholm University, personal communication), but there are most likely marine ecosystems
outside the region that sequester CO2 emissions
from the region. Basing our assumption on the
work of the IPCC, we assume that these marine
ecosystems, on average, absorb 40% of the CO2
emissions, and that the sequestering of remaining
CO2 emissions is attributed to forests. Data on CO2
emissions per capita in the region, ranging from 2 to
4.6 metric ton per year between the countries, were
derived from the World Resources Institute (WR)
(1995).
The Baltic Sea is seriously eutrophied. Various
measures have been implemented to mitigate eutrophication including use of wetlands as nutrient
sinks (for example, Fleischer and others 1991; M
Jansson and others 1994). Here, we focus on the
capacity of wetlands to filter N, assuming that all N
from human excretory release passes through sewage treatment plants with 20% or 40% purification
(Gren and others 1997), and taking into account the
relationship between nitrogen load and wetland
retention capacity (Jansson and others 1998). The
data for our estimate are based on a recent analysis
of the N-retention capacity of natural wetlands in
the BDB as a whole by using a grid cell-based GIS
approach (Jansson and others 1998). Excretory
release of N is estimated at 4 kg per person per year
(SCB 1987).
Sewage treatment plants generate P-rich sludge.
Deposition of P-rich sludge on agricultural land is a
method used in the region. Because the level of P in
Baltic region soils varies substantially, and there are
agricultural soils that are saturated with P due to
excess use of fertilizers, we use the uptake of P in
produce as a basis for our estimate of the agricultural waste assimilation footprint. Excretory release
of P is estimated at 0.5–1 kg P per person per year
(SCB 1987; Guterstam 1991). Background information for the N and P assimilation estimates is provided in Folke and others (1997).
The aggregate ecological footprint of people in the Baltic
Sea drainage basin. Previously, we estimated the
spatial dependence of the human population in the
BDB on ecosystem work. Provision of terrestrial
food, seafood, woods, and paper products at present
consumption rates was estimated separately from
absorption of CO2 emissions and excretory release
of N and P.
Ecosystems are multifunctional because each generates several services. Forests illustrate this multifunctionality by both producing timber and sequestering CO2. In an aggregate estimate of the ecological
footprint, one must account for multifunctionality,
or joint products, of an ecosystem to avoid double
counting. Therefore, we only count the largest of
the appropriated areas of the same ecosystem in our
aggregate estimate. The results of the aggregate
ecological footprint presented below are based on
those of Table 2 and include only the largest areas of
the multifunctional forest, marine, agricultural, and
wetland ecosystems. We also compare the estimates
of appropriated ecosystem areas with available ecosystem areas in the BDB.
Results on Ecosystem Appropriation
The results demonstrate that the current level of
human consumption in the BDB requires substantial support from vast terrestrial and marine ecosystems (18.7–21.4 million km2 ) greatly exceeding the
size of the Baltic Sea and its drainage basin (2.2
million km2 ). The estimates of ecosystem appropriation by people in the BDB are presented in Table 2.
Spatial ecosystem appropriation for renewable resource
production. The estimates of ecosystem appropriation for renewable resources indicate that humans
living in the BDB appropriate for their present
consumption of wood, paper, fiber, and terrestrial
food an ecosystem area that corresponds to approximately 20% of the forest area and 90% of the
agricultural land within the Baltic Sea drainage
basin. Furthermore, they require a marine ecosystem area comparable in size to three Baltic Seas to
satisfy present seafood consumption. Per capita
ecosystem appropriation for food and timber by the
average BDB citizen is estimated at approximately
20,000 m2.
Spatial ecosystem appropriation for waste assimilation.
The estimates of ecosystem appropriation for waste
assimilation indicate that humans living in the BDB
appropriate for assimilation of excretory release of N
and P an ecosystem area that corresponds to 1.8–4.5
times the present natural wetland area and 21–56%
of present agricultural land in the BDB. The human
population needs as much as 2.4–5.3 times the
present forest area in the BDB and a marine ecosystem area comparable in size to 38 Baltic Seas to
sequester carbon from CO2 emissions. This is the
case despite the fact that we account for the potential of wetlands and inland water bodies within the
121.0–263.5
1.2–2.5
53.4–116.3
53.3–116.0
307.1–668.7
128.9–280.8
130.2–283.5
47.5–103.3
80.6–175.5
111.5–242.8
135.5–295.2
92.3–200.9
753.8–1641.6
2016.1–4390.5
Agriculture
Wetland
51.7
0.7
22.8
17.4
131.1
173.1
171.1
20.3
34.4
47.6
93.4
30.7
350.5
1144.7
949.1
9.1
419.0
418.0
2408.9
1011.4
1021.1
372.3
632.1
874.7
1063.3
723.8
5913.5
15816.3
28.4
0.1
12.6
6.2
72.2
19.2
26.4
6.8
18.9
26.2
14.4
9.0
167.6
408.0
4.5–12.0
0.04–0.1
2.0–5.3
2.0–5.3
11.4–30.5
5.7–15.1
9.6–25.5
1.8–4.7
3.0–8.0
4.2–11.1
5.1–13.5
3.5–9.3
42.9–114.3
95.6–254.8
12.2–31.0
2.2
5.4–13.7
11.6–29.5
30.9–78.6
42.1
48.9–49.4
10.1–12.1
8.1–20.6
11.2–28.5
10.3–26.2
7.1–18.0
115.8–294.6
309.7–630.6
1111.9–1273.2
13.5–14.8
490.9–561.7
489.2–569.8
2857.7–3267.0
1227.1–1379.0
1256.7–1410.5
438.8–496.6
740.8–848.2
1024.6–1173.2
1225.1–1400.7
832.8–952.3
6954.6–8021.2
18664–21368
Nitrogen
Retention
Aggregate
Food
Carbon
Food
Phosphorus and Carbon Spatial
Sequestering Appropriationb
Consumption Sequestering Consumption Retention
Marine
bThe
data derived from Sweitzer and others (1996) GIS database.
column aggregate spatial appropriation is not the sum of the row total because the estimates of forests, marine, and agricultural ecosystems areas each concerns more than one ecosystem service. To avoid double counting, only the largest
area of respective ecosystem is counted.
aPopulation
6.8
0.2
3.0
1.8
17.3
37.3
35.8
2.7
4.5
6.3
6.3
3.1
38.1
163.2
4004
34
1768
1779
10162
5045
8512
1570
2667
3690
4511
3099
38,101
84,942
Belarussia
Norway
Ukraine
Czech Republic
Russia
Finland
Sweden
Estonia
Latvia
Lithuania
Denmark
Germany
Poland
Total
1.2
0.9
0.1
0.05
38.6
25.5
30.1
2.1
1.1
1.0
1.6
0.6
3.9
106.8
Wood
Carbon
Populationa Carbon
Sequestering Consumption Sequestering
⫻103
Country
Inland Water Forest
Spatial Ecosystem Appropriation (km2 y⫺1 ⫻ 103)
Table 2. Human Population and Spatial Ecosystem Appropriation in the Baltic Sea Drainage Basin by Ecosystem Service and Country
Freshwater, Ecological Footprints, and Ecosystem Services
355
356
Å. Jansson and others
Figure 2. Spatial ecosystem
appropriation of ecosystem
services per capita in the Baltic
Sea drainage basin.
BDB to act as carbon sinks. The per capita waste
assimilation footprint is estimated at 215,000–
250,000 m2, an order of magnitude larger than the
one for renewable resource appropriation. Seventyfive to 86% of the waste assimilation footprint is
attributed to carbon sequestering by marine systems
external to the BDB.
We present the results of nitrogen retention and
carbon sequestering of wetlands in one column
(Table 2) because in some cases sequestering was
larger than retention, and in others the result was
vice versa. To avoid double counting, we have not
added sequestering and retention but consistently
have used the largest of the two.
The aggregate ecological footprint of people in the Baltic
Sea drainage basin. The ecological footprint of the
total human population in the BDB corresponds to
an area as large as 8.5–9.5 times the whole Baltic
Sea and its drainage basin. The terrestrial part of this
appropriation is similar to half the size of the United
States (including Alaska and Hawaii) and the marine to approximately 15% of the size of the Atlantic
Ocean.
The total appropriation of terrestrial and marine
ecosystems per capita in the BDB is estimated at
220,000–250,000 m2, which corresponds to approximately 260–300 tennis courts. The spatial appropriation per capita divided into provision of resources
and waste assimilation services is shown in Figure 2.
The requirements for ecosystem support seem huge.
Nevertheless, the estimate seems conservative be-
cause we have quantified only the spatial capacity of
some ecosystems to produce some ecosystem services used by the human population of the BDB.
HUMAN DEPENDENCE ON FRESH WATER
FOR ECOSYSTEM SERVICES
Freshwater use in human society and freshwater
demand for the generation of ecosystem services is
seldom analyzed simultaneously. The liquid fresh
water appearing as runoff in rivers, lakes, and
aquifers (Falkenmark and Mikulski 1994), and used
directly in human activities for drinking water,
industrial purposes, and agricultural irrigation
(Gleick 1993), has received much attention in the
debate over water scarcity (UN 1997). Postel and
Carpenter (1997) have identified a number of ecosystem services derived from rivers and lakes, and
other articles investigate the role of fresh water in
ecosystem performance (for example, Covich 1993;
Gunderson and others 1995a).
However, water vapor from terrestrial ecosystems
for ecosystem services has received less attention
(Figure 3), particularly in global freshwater assessments. Its use in food production has been accounted for partly in global freshwater budgets
(Postel and others 1996; Pimentel and others 1997)
and to some extent in rain-fed agriculture (Postel
1998) in developing countries (Rockström and others 1998). Savenije (1995) analyzed moisture recycling through evapotranspiration in the Sahel, and
Freshwater, Ecological Footprints, and Ecosystem Services
357
Figure 3. The relationship between precipitation, water vapor
flow (evapotranspiration), and
liquid water flow (runoff ) in a
forest ecosystem.
recently, Hutjes and others (1998) addressed interactions between the biosphere–atmosphere and hydrological processes at different scales. Redirections
from water vapor to liquid water flows and the
reverse have been analyzed in relation to deforestation (for example, Hornbeck and others 1997; Lal
1997) and invasion of alien tree species at the
watershed level (for example, van Wilgen and
others 1996).
Below we will estimate the water vapor flow that
people in the BDB depend upon for ecosystem
support. We derive the estimate by quantifying
water vapor flow from the ecological footprints of
forests, wetlands, inland water bodies, and agriculture, arrived at in the first section. This water vapor
flow reflects the work of nature required for generation of ecosystem services appropriated by the human population in the BDB. We also will quantify
the liquid water appropriation by the BDB’s human
population.
Methods
Liquid water appropriation. The estimate of liquid
water appropriation includes domestic/household
(drinking water, homes, commercial establishments, and public services) and industrial withdrawals as classified by WRI (1995). Freshwater use on a
country basis was derived from WRI (1995) and
adjusted for the population of each country living
within the BDB.
Water vapor dependence. The estimate of water
vapor dependence of people in the BDB includes
water vapor flows from the ecological footprint of
forests, wetlands, and inland water bodies. It also
includes water vapor flows from the agricultural
footprint (rain-fed and irrigated production as well
as pasture) and water consumption by cattle. The
Table 3. Evapotranspiration Data of Forests,
Wetlands, and Inland Water Bodies
Biome
ET
Forest
Taiga
Mixed
Wetlanda
400
mm y⫺1
500
mm y⫺1
200–1020 mm y⫺1
Inland waters 508,500
aThe
Unit
m3km⫺2y⫺1
Reference
Falkenmark (1989b)
Falkenmark (1989b)
Rockström and
others (1999)
Ljungemyr (Pers.
comm.)
interval includes ET data for both bogs and fens.
estimate began with the composition of ecosystems
in the BDB and their water vapor flows. Water
vapor flow of the forest footprint was based on
evapotranspiration data of taiga and mixed forest.
Water vapor flow of wetlands was derived from
evapotranspiration data for bogs and fens. Ninetysix percent of BDB wetlands are bogs and fens
(Aselmann and Crutzen 1989). We used annual
evaporation from lakes as an approximation of
evaporation from inland water bodies. The annual
mean evaporation from inland freshwater lakes in
the BDB was estimated for 1979–1994. This was
made possible through modeling of data derived
from a meteorological database (P. Ljungemyr, SMHI,
Norrköping, Sweden). Data and sources of information on water vapor flow of forests, wetlands, and
inland water bodies are provided in Table 3.
Water vapor flow in agriculture was estimated for
cropland and pasture. We multiplied crop yields
from the different crops grown in each country in
the BDB (FAO 1997) with water requirement data
358
Å. Jansson and others
Table 4. Water Use Efficiencies of Different Crops and Grasses within the Baltic Sea Drainage Basin
Crop
Grain b
Wheat
Barley
Wheat
Wheat
Barley
Barley
Barley
Mean
Legumesc
Cabbage
Pea
Lens
Lucern
Clover
C3
Sunflower
Mean
Potatoes d
Mean
Sugar beets c
Mean
Grasses c
Mean
WUE a
(m3 ton⫺1 )
1131
539
787
964
640
652
1188
843 ⫾ 158
518
569
204.5
171.53
312
571
623
424 ⫾ 133
296
402
305
334 ⫾ 67
213
168
377
253 ⫾ 125
900
780
790.91
429.18
1031.3
618.75
758 ⫾ 169
Comment
Reference
Entz and Fowler (1991)
Andersen and others (1992)
Imtiyaz and others (1982)
Imtiyaz and others (1982)
Imtiyaz and others (1982)
Imtiyaz and others (1982)
Lòpez-Castaneda and Richards (1994)
Irrigated
Nonirrigated
Irrigated
Nonirrigated
Brassica oleracea
Vigna sinensis Endl
Lens culinaris
Medicago sativa
Nonirrigated
Bean, soya, sunflower
Helianthus annuus
Black (1971)
Black (1971)
Johnsson (1994)
Johnsson (1994)
Oliva and others (1994)
Hattendorf and others (1988)
Black (1971)
June–Aug
June–Aug
June–Aug
Tanner (1981)
Tanner (1981)
Tanner (1981)
Irrigated
Nonirrigated
Beta vulgaris
Brown and others (1987)
Brown and others (1987)
Black (1971)
Stenotaphrum secundatum
Dactylis glomerata
Festuca arundinacea
Festuca arundinacea
Lolium perenne
Lolium multiflorum
Shih and Snyder (1985)
Thomas (1994)
Thomas (1994)
Johnsson (1994)
Thomas (1994)
Thomas (1994)
aWUE,
water use efficiencies; 95% confidence interval.
on grain yield.
cBased on dry mass.
dBased on dry mass. Does not include roots and leaves.
bBased
for different crops (Table 4). For each crop we
calculated the percentage area of the total agricultural area in each BDB country (FAO 1997). We
then assumed equal crop percentage areas for the
drainage basin as for the country of concern. Crop
and yield data (hg/ha) for the different countries in
the BDB were derived from FAO Statistics Agrostat
(1997). From the same database we also derived
information on amount of fodder grown on pastures. We used estimates of water use efficiency of
grasses (Table 4) as an approximation of water use
in pasture. Water consumption by cattle was derived from IDWR (1998) and number of cattle in the
BDB countries from the FAO database (1997, data
from 1996). The data in Tables 3 and 4 are related to
the estimate of spatial ecosystem appropriation by
people in the BDB, to arrive at the estimate of
human dependence on invisible water vapor flows.
The inflow of renewable fresh water into the BDB
was estimated as annual precipitation by country,
adjusting for the part of the country located within
the BDB.
Results on Freshwater Dependence
People in the BDB depend on a flow of water vapor
31–77 times (approximately 54) the amount of
managed liquid fresh water in society (Figure 4) for
their appropriation of ecosystem services. This fresh-
Freshwater, Ecological Footprints, and Ecosystem Services
359
Figure 4. Per capita dependence on water vapor flows
that make possible the appropriation of ecosystem
services derived from forests, croplands, wetlands,
and inland water bodies.
Table 5. Annual Precipitation and Its Allocation between Human Direct Use and Ecosystem Requirements
of Fresh Water within the Baltic Sea Drainage Basin
Country
Population
⫻103
Annual
Precipitation
(km3 )
Direct Use
(km3 y⫺1 )a
Crops
(km3 y⫺1 )
Forests
(km3 y⫺1 )
Wetlands
(km3 y⫺1 )
Inland Waters
(km3 y⫺1 )
Belarussia
Norway
Ukraine
Czech. (former)
Russia
Finland
Sweden
Estonia
Latvia
Lithuania
Denmark
Germany
Poland
Total
4.004
34
1.768
1.779
10.162
5.045
8.512
1.570
2.667
3.690
4.511
3.099
38.101
84.942
45–90 b
7–14 b
7–14 b
5–10 b
164–328 b
136–197 c
263–350 d
23–46 b
33–65 b
33–66 b
23–34 e
14–20 f
177–203 g
930–1437
0.95
0.02
0.83
0.61
6.16
2.96
2.73
3.18
0.60
4.22
0.59
1.70
12.99
37.54
10.8
0.1
2.1
1.5
3.7
3.0
4.7
2.2
2.3
5.5
11.9
9.1
50.7
107.6
11.9
2.8
1.6
2.0
64.6
84.7
116.3
11.3
12.9
7.3
0.4
1.6
33.4
350.8
0.8–3.8
0.4–2.3
0
0
2.3–11.9
8.4–42.9
9.8–49.9
2.0–10.3
0.6–3.2
0.3–1.6
0.1–0.6
0.1–0.6
2.6–13.4
27.4–140.5
0.6
0.5
0.0
0.0
19.6
13.0
15.3
1.1
0.6
0.5
0.8
0.3
2.0
54.3
aWRI
(1994).
from van der Leeden and others (1990).
cDerived from Statistical Yearbook of Finland (1991).
dDerived from SCB (1990) Naturmiljön i Siffror.
eDerived from Statistical Yearbook of Denmark (1995).
fDerived from Statistical Yearbook of Germany (1996).
gDerived from State Inspectorate for Environmental Protection, Environmental Information Center Grid-Warsaw, UNEP (1993). State of Environment in Poland.
bDerived
water demand by BDB inhabitants for food, timber,
and for assimilation of CO2 and partial N and P
emissions is estimated at more than twice the
amount of annual rainfall in the BDB.
Allocation of precipitation in the BDB. The data on
annual precipitation are presented in Table 5. According to our estimate, humans directly appropriate only 3%–4% of annual precipitation in the
basin. However, freshwater use by forests, wetlands,
agricultural land, and inland water bodies corresponds to 38%–71% of annual precipitation in the
BDB (Figure 5). Hence, the terrestrial systems and
inland water bodies within the BDB need approximately 15 times more renewable fresh water than
the direct human freshwater appropriation. The
estimates indicate that 24%–38% of the annual
360
Å. Jansson and others
Figure 5. Allocation of precipitation over the Baltic Sea drainage
basin.
Table 6. Annual Liquid Water Flow Appropriation and Water Vapor Flow Dependence by People in the
Baltic Sea Drainage Basin
Country
Human Direct
Consumption a
Forest b
Agriculture c
Wetland d
Inland
Waters e
Belarussia
Norway
Ukraine
Czech. (former)
Russia
Finland
Sweden
Estonia
Latvia
Lithuania
Denmark
Germany
Poland
Total
0.95
0.02
0.83
0.61
6.16
2.96
2.73
3.18
0.60
4.22
0.59
1.70
12.99
37.54
60.5–131.7
0.5–1.0
26.7–58.2
26.6–58.0
122.8–267.5
51.6–112.3
52.1–113.4
23.7–51.7
40.3–87.7
55.8–121.4
67.8–147.6
46.1–100.5
376.9–820.8
951.4–2071.8
10.8
0.1
2.1
1.5
3.7
3.0
4.7
2.2
2.3
5.5
11.9
9.1
50.7
107.6
2.4–31.6
0.4–2.3
1.1–13.9
1.1–14.0
6.2–80.1
8.4–42.9
9.8–50.3
2.0–12.4
1.6–21.0
2.2–29.1
2.1–26.7
1.4–18.3
23.2–300.5
61.9–643.2
0.6
0.5
0.0
0.0
19.6
13.0
15.3
1.1
0.6
0.5
0.8
0.3
2.0
54.3
renewable freshwater appropriation (km3 y⫺1 ). Source: WRI (1994).
needed to support appropriated area (km3 y⫺1 ).
cWater needed to support present production (km3 y⫺1 ).
dWater needed to support appropriated area (km3 y⫺1 ).
eWater needed to support appropriated area (km3 y⫺1 ).
aDirect
bWater
precipitation is appropriated by forests, 2%–15% by
natural wetlands, and 4%–6% by inland water
bodies, and 8%–12% is needed in agricultural
biomass production, and 0.2% is consumed by
livestock. The nonquantified 25%–59% of the freshwater flow presumably is attributed to groundwater
recharge and river runoff.
Liquid water appropriation and water vapor dependence by people in the BDB. The estimates presented
in Table 6 show the amount of fresh water that
people of the BDB consume in households and
industries. Human dependence on fresh water is
also revealed by the appropriation of spatial ecosystem areas for ecosystem services (Table 2 and Figure
Freshwater, Ecological Footprints, and Ecosystem Services
2). Not surprisingly, the fresh water needed to
support the appropriation of the forest footprint for
carbon sequestering (including timber production)
dominates the water vapor flow dependence (950–
2072 km3 y⫺1 ). This invisible water dependence is
25–55 times larger than human liquid water appropriation. The BDB people’s total dependence on
water vapor flow is estimated at 1175–2877 km3
y⫺1, and the total dependence on renewable fresh
water (liquid and vapor) is at 1213–2915 km3 y⫺1.
The estimated per capita ecological footprint of
forests, wetlands, agricultural land, and inland water bodies of 220,000–250,000 km2 y⫺1 requires
approximately 13,835–33,870 m3 of fresh water
annually (Figure 4). Without renewable fresh water
the capacity of these ecosystems to generate the
ecological services of terrestrial food and timber
production and assimilation of CO2 emissions and
human excretory release of nutrients would deteriorate and cease to exist. The water vapor flow
dependence for ecosystem services is estimated as
approximately 54 (31–77) times the amount of
liquid water flow appropriated in society.
External freshwater dependence. The average annual precipitation in the BDB region is approximately 1200 km3 (Table 5) or approximately 30
times the liquid water appropriation in society. The
average water vapor dependence of people in the
BDB for ecosystem services from terrestrial and
inland water systems is approximately 2100 km3
y⫺1. The BDB forests, wetlands, inland water bodies,
and agricultural ecosystems of concern here do not
require all precipitation (38–71%; Figure 5). Therefore, the demand by BDB inhabitants for water
vapor flow of ecosystems is more than twice the
annual precipitation in the BDB, assuming similar
evapotranspiration and water use efficiency values
as used in our estimates (Tables 3 and 4). This
substantial amount of renewable freshwater flow
for ecosystem services, far out of sight and perception of citizens of the BDB, is needed to sustain their
present standards of living.
DISCUSSION
We have estimated that the human population in
the BDB appropriates vast ecosystem areas to satisfy
the demand for food, wood, paper, fibers, seafood,
CO2 assimilation, and partial P and N retention.
Altogether our estimates indicate that this demand
appropriates ecosystem areas approximately 8.5–
9.5 times the size of the Baltic Sea and its drainage
basin. The bulk of the ecological footprint is attributed to carbon sequestering by oceans and forests
(Figure 2).
361
The footprint estimate presented here is a static
picture of the present situation and consequently
does not account for ecosystem dynamics, technological, or other change. It is a snapshot of ecosystem demand for nature’s services by people in the
BDB. The ecological footprint as performed here
reflects the area wherein the essential work of the
ecosystem is done but does not address internal
dynamics.
The objective of our ecological footprint analysis
is somewhat different from that of Rees and Wackernagel (1994). Their objective was to estimate the
share of global resources appropriated by a certain
human population/activity. The purpose of our
analysis is simply to make visible the necessary
work of ecosystems, including biodiversity, for generation of essential ecosystem services that humanity depends upon (Folke and Kautsky 1989; Folke
and others 1997, 1998).
Trade between nations makes possible the appropriation of ecosystems from other regions for food
and seafood. Of the renewable resources, only the
demand for seafood within the BDB requires larger
areas than available within the region. In terms of
food and timber trade, the region is not necessarily a
major consumer of ecosystems of other regions.
Therefore, the BDB’s trade footprint does not reduce available terrestrial ecosystem support to other
regions, unless production methods involved in
imported food and timber for the region erodes the
capacity of ecosystems in exporting nations to generate services, or transportation of traded goods itself
causes costly impacts (Andersson and others 1995).
Emissions behind the waste footprint are not
traded, at least not so far. However, the web of
human activities in industrial society, of which trade
is a part, causes emissions. The size of the waste
footprint indicates the widespread ‘‘hidden demand’’ of industrial society for ecosystem support
extending beyond national borders. The need to
address environmental and socioeconomic effects of
transboundary impacts of waste emissions has long
been recognized in science and policy, reflected in
various conventions and international agreements.
But, the need to address land-use change in one
region causing transboundary impacts on ecosystems’ capacity to generate the ecological footprint
support in other regions is still largely unrecognized.
Examples include habitat degradation that eliminates ‘‘mobile links’’ like fish and birds that perform
important functions in several ecosystems (Baskin
1997; Post and others 1998; Holmlund and Hammer
1999).
Are there any potential mechanisms to reduce the
footprint? Dixon (1998) estimates that, theoreti-
362
Å. Jansson and others
cally, silvicultural practices can sequester substantial
amounts of carbon. There is also the option of
increasing the present forested area, but focusing on
carbon sequestering alone may have impacts on
other ecosystem services, such as crop production or
wetland conservation. Planting trees out of context
for carbon sequestering is treating the symptom
rather than correcting the cause. Ultimately, a decrease in CO2 emissions from industrial society is
necessary (Houghton and others 1996).
According to our footprint estimates there are not
enough wetlands in the region to assimilate excretory N release from the human population in the
basin. But wetlands can nevertheless provide a
cost-effective complement to conventional sewage
treatment, partly due to their potential in processing
nonpoint source pollution (Gren 1995). However,
wetlands in the BDB seldom are located in the
vicinity of urban areas (Sweitzer and others 1996).
Unless wetlands are created adjacent to urban areas,
using wetlands for nutrient retention of excretory N
discharges requires transportation. Transportation is
also an issue in disposal of P-rich sludge from
sewage treatment plants on agricultural areas and
may increase the demand for carbon sequestering.
Reducing footprints by focusing on one service at
a time will not be effective. Ecosystems are multifunctional, that is, several services are generated by
each system. The multifunctionality is linked to
other systems through complex interactions among
the biota and biogeochemical flows, and as we have
illustrated by hydrological flows.
Terrestrial ecosystems, including inland water
bodies, represent less than 15%–25% of the spatial
appropriation for ecosystem services by people in
the BDB. However, our estimates illustrate that the
human appropriation of ecosystem services from
these systems requires substantial quantities of water vapor flows. Water vapor dependence is estimated at as much as 1175–2875 km3 annually, or 54
times the human use of liquid water flows in
households and industries within the region (Table
6 and Figure 4). These invisible freshwater flows
support the work of ecosystems in other regions
that generate ecosystem services demanded by the
present standard of living in the BDB. The inhabitants of the BDB depend on approximately twice as
much invisible fresh water than the annual precipitation asset of their own region. This aspect of
human freshwater dependence has been largely
neglected in global freshwater assessments (for example, UN 1997).
It may be argued that our estimate exaggerates
freshwater needs, because we use measures of
evapotranspiration, not only transpiration. However, water vapor flows also may be of ecological
importance even if not directly transpired by plants
in the system. For example, there are ecosystems
that require the cooling effect of evaporation to
function (for example, Baskin 1997). The biota also
can play an important role in the regulation of
atmospheric water by redirecting liquid water flows
to water vapor flows thereby recycling it to local
rainfall (for example, Savenije 1995). The necessity
of fresh water for ecosystem services of rivers and
coastal systems has not been addressed in this
article, but Postel and Carpenter (1997) provide a
comprehensive overview.
Available and high-quality fresh water will become one of the major scarce resources in the future
(Lundqvist 1998); it, indeed, already has in many
parts of the world (Falkenmark 1989a). The whole
population in the BDB probably will not suffer from
shortage of fresh water in the foreseeable future due
to climatic reasons. But there are areas within the
BDB where land-use change has caused water
quantity problems (Zucchetto and Jansson 1985),
and contamination of fresh water in the region is a
severe problem. Many areas within the BDB suffer
from contamination of groundwater, with concentrations of toxic substances exceeding limits specified by drinking water guidelines (for example,
Niemczynowicz 1993).
There always will be a trade-off between the use
of available fresh water by households, industry,
and irrigation—the visible liquid water—and use for
the generation of ecosystem services—the invisible
water vapor. For example, redirection of water
flows for increased crop production via irrigation
has generated both quantitative and qualitative
change in adjacent ecosystems (Postel 1992), but
such change is seldom accounted for until the
impact is visible. Land-use change, such as urbanization or deforestation, in one country may redirect
freshwater flows in a fashion that erodes the capacity of ecosystems in another country to generate
essential services required by its people. Hence,
redirection of fresh water in the landscape through
land-use change also may cause transboundary
impacts. To avoid costly side effects and to reduce
the risk of unintentional impacts of partial management, such land-use change should be acknowledged and the trade-off between liquid water use
and water vapor use should be made with the
Freshwater, Ecological Footprints, and Ecosystem Services
broadest possible analysis of all important components and interactions.
CONCLUSIONS
Our estimates indicate that the spatial ecosystem
appropriation—the ecological footprint—by people
living within the BDB drainage basin is very large.
Although our estimate of the ecological footprint
analysis may be criticized, it illustrates that the work
of nature in supporting social and economic development is significant.
Obviously, the value of nature’s work is not only a
matter of amenity, as has been the focus of preference-based economic valuation of nature, particularly in the US. The analysis illustrates that huge
ecosystem areas are required for the generation of
ecosystem services. A complex web of interactions
between a diversity of plants, animals, microorganisms, and their biogeochemical and hydrological
environments sustains the flow of these services.
Humans often are not aware of their uses of
critical ecosystem services or their dependence on
ecosystem support. The demand for this support is
‘‘mentally hidden’’ to large segments of society; it
has no price in the market and is too seldom
accounted for in decision making. We have argued
elsewhere that there are many ecosystem services
that meet the criteria of having economic value
(they contribute to well-being and are scarce) but
for which humans have not developed preferences
(Costanza and Folke 1997). Ecological considerations will receive low priority if people and policymakers do not understand why they should care
about ecosystem support and the interactions with
the biogeochemical/hydrological flows. Accounting
for ecosystem support is not just a matter of adding a
few external monetary costs here and there. It is a
matter of basic life-support conditions for human
societies. Viewing the social and economic subsystem in its proper perspective relative to the
ecosphere is crucial for moving human society
towards a more sustainable relationship with its
environmental resource base. Therefore ecosystem
services and the work of nature behind these services need to be made visible, a major objective of
our footprint analysis.
Similarly, the critical links between water vapor
flows and ecosystem services need to be made
visible. Terrestrial and inland-water ecosystems
would not be able to continuously generate services
without a flow of renewable fresh water. Our
analysis illustrates that the generation and maintenance of the work of nature—the ecological foot-
363
print—for ecosystem services requires substantial
amounts of water vapor flows to maintain the
standard of living of people in the BDB.
Given the expansion of the human dimension on
earth, there is a risk for a potential and unperceived
scarcity of water vapor flows for ecosystem services.
We stress the necessity of capturing the water needs
of ecosystems both in renewable freshwater management and assessment, as well as in ecosystem
management. Although links between freshwater
flows and ecosystem services have been understood
and intentionally managed in some areas and watersheds (for example, Gunderson and others 1995a;
van Wilgen and others 1996), unintentional side
effects of upstream land-use change on downstream
resource-dependent activities seem to be more the
rule than the exception. Such side effects generally
are caused by partial management focusing on
enhancing the flow of a particular resource at the
expense of other invisible ecosystem services in the
watershed with subsequent social and economic
consequences.
An engineering approach to water issues that
does not fully perceive the complex dynamics and
interdependencies of living systems and water flows
seems to dominate the picture. We advocate a
dynamic ecohydrological landscape-management
perspective, where the interactions within and between ecosystems, hydrology, and human activities
upstream to downstream in watersheds are explicitly accounted for to the fullest extent possible.
Natural sciences information will not be sufficient
for appropriate management. It has to be complemented by proper institutional design (Hanna and
others 1996), where adaptive management may
play an important role (Gunderson and others
1995b; Walters 1997; Berkes and Folke 1998).
There are lessons from the real world for how to
improve management of the ecohydrological landscape and design institutions that work in synergy
with ecosystem processes and functions. Complex
cross-scale institutional management of irrigation
systems for a diversity of human uses is well known
(Ostrom 1990; Lansing 1991; Mabry 1996). As well,
there has been sophisticated watershed–ecosystembased management of ancient societies (Berkes and
others 1998), and recently water–ecosystem services restoration by local communities at the watershed level has been initiated (Goldsmith 1998).
ACKNOWLEDGMENTS
We are grateful for constructive comments from two
anonymous referees, Malin Falkenmark, Sandra
Postel, and Sindre Langaas. C.F.’s work was partly
364
Å. Jansson and others
supported by the Pew Scholars Program in Conservation and the Environment of the Pew Charitable
Trusts, and LG’s from the Swedish Council for
Forestry and Agricultural Research (SJFR).
de Groot RS. 1992. Functions of nature. Amsterdam: WoltersNoordhoff.
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