Human Domination of Earth’s Ecosystems
Peter M. Vitousek, Harold A. Mooney, Jane Lubchenco, Jerry M. Melillo
Human alteration of Earth is substantial and growing. Between one-third and one-half
of the land surface has been transformed by human action; the carbon dioxide con-
centration in the atmosphere has increased by nearly 30 percent since the beginning of
the Industrial Revolution; more atmospheric nitrogen is fixed by humanity than by all
natural terrestrial sources combined; more than half of all accessible surface fresh water
is put to use by humanity; and about one-quarter of the bird species on Earth have been
driven to extinction. By these and other standards, it is clear that we live on a human-
dominated planet.
All organisms modify their environment,
and humans are no exception. As the hu-
man population has grown and the power of
technology has expanded, the scope and
nature of this modification has changed
drastically. Until recently, the term “hu-
man-dominated ecosystems” would have
elicited images of agricultural fields, pas-
tures, or urban landscapes; now it applies
with greater or lesser force to all of Earth.
Many ecosystems are dominated directly by
humanity, and no ecosystem on Earth’s sur-
face is free of pervasive human influence.
This article provides an overview of hu-
man effects on Earth’s ecosystems. It is not
intended as a litany of environmental disas-
ters, though some disastrous situations are
described; nor is it intended either to down-
play or to celebrate environmental success-
es, of which there have been many. Rather,
we explore how large humanity looms as a
presence on the globe—how, even on the
grandest scale, most aspects of the structure
and functioning of Earth’s ecosystems can-
not be understood without accounting for
the strong, often dominant influence of
humanity.
We view human alterations to the Earth
system as operating through the interacting
processes summarized in Fig. 1. The growth
of the human population, and growth in the
resource base used by humanity, is main-
tained by a suite of human enterprises such
as agriculture, industry, fishing, and inter-
national commerce. These enterprises
transform the land surface (through crop-
ping, forestry, and urbanization), alter the
major biogeochemical cycles, and add or
remove species and genetically distinct pop-
ulations in most of Earth’s ecosystems.
Many of these changes are substantial and
reasonably well quantified; all are ongoing.
These relatively well-documented changes
in turn entrain further alterations to the
functioning of the Earth system, most no-
tably by driving global climatic change (1)
and causing irreversible losses of biological
diversity (2).
Land Transformation
The use of land to yield goods and services
represents the most substantial human al-
teration of the Earth system. Human use of
land alters the structure and functioning of
ecosystems, and it alters how ecosystems
interact with the atmosphere, with aquatic
systems, and with surrounding land. More-
over, land transformation interacts strongly
with most other components of global en-
vironmental change.
The measurement of land transforma-
tion on a global scale is challenging; chang-
es can be measured more or less straightfor-
wardly at a given site, but it is difficult to
aggregate these changes regionally and glo-
bally. In contrast to analyses of human al-
teration of the global carbon cycle, we
cannot install instruments on a tropical
mountain to collect evidence of land trans-
formation. Remote sensing is a most useful
technique, but only recently has there been
a serious scientific effort to use high-resolu-
tion civilian satellite imagery to evaluate
even the more visible forms of land trans-
formation, such as deforestation, on conti-
nental to global scales (3).
Land transformation encompasses a
wide variety of activities that vary sub-
stantially in their intensity and conse-
quences. At one extreme, 10 to 15% of
Earth’s land surface is occupied by row-
P. M. Vitousek and H. A. Mooney are in the Department
of Biological Sciences, Stanford University, Stanford, CA
94305, USA. J. Lubchenco is in the Department of Zool-
ogy, Oregon State University, Corvallis, OR 97331,
USA. J. M. Melillo is at the U.S. Office of Science and
Technology Policy, Old Executive Office Building, Room
443, Washington, DC 20502, USA.
Fig. 1. A conceptual
model illustrating hu-
manity’s direct and indi-
rect effects on the Earth
system [modified from
(56)].
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crop agriculture or by urban-industrial ar-
eas, and another 6 to 8% has been con-
verted to pastureland (4); these systems
are wholly changed by human activity. At
the other extreme, every terrestrial ecosys-
tem is affected by increased atmospheric
carbon dioxide (CO
2
), and most ecosys-
tems have a history of hunting and other
low-intensity resource extraction. Be-
tween these extremes lie grassland and
semiarid ecosystems that are grazed (and
sometimes degraded) by domestic animals,
and forests and woodlands from which
wood products have been harvested; to-
gether, these represent the majority of
Earth’s vegetated surface.
The variety of human effects on land
makes any attempt to summarize land trans-
formations globally a matter of semantics as
well as substantial uncertainty. Estimates of
the fraction of land transformed or degraded
by humanity (or its corollary, the fraction of
the land’s biological production that is used
or dominated) fall in the range of 39 to 50%
(5) (Fig. 2). These numbers have large un-
certainties, but the fact that they are large is
not at all uncertain. Moreover, if anything
these estimates understate the global im-
pact of land transformation, in that land
that has not been transformed often has
been divided into fragments by human al-
teration of the surrounding areas. This frag-
mentation affects the species composition
and functioning of otherwise little modified
ecosystems (6).
Overall, land transformation represents
the primary driving force in the loss of
biological diversity worldwide. Moreover,
the effects of land transformation extend
far beyond the boundaries of transformed
lands. Land transformation can affect cli-
mate directly at local and even regional
scales. It contributes ;20% to current
anthropogenic CO
2
emissions, and more
substantially to the increasing concentra-
tions of the greenhouse gases methane and
nitrous oxide; fires associated with it alter
the reactive chemistry of the troposphere,
bringing elevated carbon monoxide con-
centrations and episodes of urban-like
photochemical air pollution to remote
tropical areas of Africa and South Amer-
ica; and it causes runoff of sediment and
nutrients that drive substantial changes in
stream, lake, estuarine, and coral reef eco-
systems (7–10).
The central importance of land trans-
formation is well recognized within the
community of researchers concerned with
global environmental change. Several re-
search programs are focused on aspects of
it (9, 11); recent and substantial progress
toward understanding these aspects has
been made (3), and much more progress
can be anticipated. Understanding land
transformation is a difficult challenge; it
requires integrating the social, economic,
and cultural causes of land transformation
with evaluations of its biophysical nature
and consequences. This interdisciplinary
approach is essential to predicting the
course, and to any hope of affecting the
consequences, of human-caused land
transformation.
Oceans
Human alterations of marine ecosystems
are more difficult to quantify than those of
terrestrial ecosystems, but several kinds of
information suggest that they are substan-
tial. The human population is concentrat-
ed near coasts—about 60% within 100
km—and the oceans’ productive coastal
margins have been affected strongly by
humanity. Coastal wetlands that mediate
interactions between land and sea have
been altered over large areas; for example,
approximately 50% of mangrove ecosys-
tems globally have been transformed or
destroyed by human activity (12). More-
over, a recent analysis suggested that al-
though humans use about 8% of the pri-
mary production of the oceans, that frac-
tion grows to more than 25% for upwelling
areas and to 35% for temperate continen-
tal shelf systems (13).
Many of the fisheries that capture ma-
rine productivity are focused on top pred-
ators, whose removal can alter marine eco-
systems out of proportion to their abun-
dance. Moreover, many such fisheries
have proved to be unsustainable, at least
at our present level of knowledge and
control. As of 1995, 22% of recognized
marine fisheries were overexploited or al-
ready depleted, and 44% more were at
their limit of exploitation (14) (Figs. 2
and 3). The consequences of fisheries are
not restricted to their target organisms;
commercial marine fisheries around the
world discard 27 million tons of nontarget
animals annually, a quantity nearly one-
third as large as total landings (15). More-
over, the dredges and trawls used in some
fisheries damage habitats substantially as
they are dragged along the sea floor.
A recent increase in the frequency,
extent, and duration of harmful algal
blooms in coastal areas (16) suggests that
human activity has affected the base as
well as the top of marine food chains.
Harmful algal blooms are sudden increases
in the abundance of marine phytoplank-
ton that produce harmful structures or
chemicals. Some but not all of these phy-
toplankton are strongly pigmented (red or
brown tides). Algal blooms usually are
correlated with changes in temperature,
nutrients, or salinity; nutrients in coastal
waters, in particular, are much modified by
human activity. Algal blooms can cause
extensive fish kills through toxins and by
causing anoxia; they also lead to paralytic
shellfish poisoning and amnesic shellfish
poisoning in humans. Although the exis-
tence of harmful algal blooms has long
been recognized, they have spread widely
in the past two decades (16).
Fig. 2. Human domi-
nance or alteration of
several major compo-
nents of the Earth sys-
tem, expressed as (from
left to right) percentage
of the land surface trans-
formed (5); percentage
of the current atmo-
spheric CO
2
concentra-
tion that results from hu-
man action (17 ); per-
centage of accessible
surface fresh water used (20); percentage of terrestrial N fixation that is human-caused (28); percentage
of plant species in Canada that humanity has introduced from elsewhere (48); percentage of bird
species on Earth that have become extinct in the past two millennia, almost all of them as a conse-
quence of human activity (42); and percentage of major marine fisheries that are fully exploited,
overexploited, or depleted (14).
1
9
5
1
0
20
40
60
80
100
1
9
5
5
1
9
6
0
1
9
6
5
1
9
7
0
1
9
7
5
1
9
8
0
1
9
8
5
1
9
9
0
1
9
9
4
Year
R
e
s
o
u
r
c
e
s

(
%
)
Phase IV-
Senescent
Phase III-
Mature
Phase II-
Developing
Phase I-
Undeveloped
Fig. 3. Percentage of major world marine fish
resources in different phases of development,
1951 to 1994 [from (57 )]. Undeveloped 5 a low
and relatively constant level of catches; develop-
ing 5 rapidly increasing catches; mature 5 a high
and plateauing level of catches; senescent 5
catches declining from higher levels.
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HUMAN-DOMINATED ECOSYSTEMS:ARTICLES