Method Précis: Human Appropriation of Net Primary
Production (HANPP)
Helmut Haberl
The human appropriation of net primary production(HANPP) is an indicator of
the intensity of the colonization of ecosystems, namely, the intensity of land use.
HANPP is based on the quantification of human interventions in energy flows in
ecosystems or, more precisely, in net primary production and the availability of the
products of net primary production (primarily biomass) in ecosystems.
Net primary production (NPP) is a measure of the quantity of organic material
produced by plants through photosynthesis from inorganic materials. In energetic
terms, photosynthesis involves the transformation of radiant energy from the sun
into energy stored in chemical compounds. This energy is initially stored in the
biomass of plants and then either accumulates in the ecosystem or serves as food
energy for humans, animals, fungi and some microorganisms (so-called ‘heterotrophic’
organisms). During photosynthesis, CO2 is absorbed from the atmosphere
and stored in a variety of chemical compounds in biomass. If this energy is
released, for example, through combustion or the metabolism of heterotrophic
organisms (‘respiration’), then carbon is released into the atmosphere in the form
of CO2. In the short term, ecosystems may represent a ‘carbon sink’ (that is,
absorb more CO2 through photosynthesis than flows back to the atmosphere due to
respiration and combustion) or a ‘carbon source’ (CO2 outflows exceed photosynthesis).
In the long term and across larger areas, the average absorption and release
of CO2 from ecosystems is largely balanced;6 that is, CO2 inflows equal CO2 outflows
(Körner 2009). NPP is an important process in ecosystems; it supplies the
entire food energy for humans and all other heterotrophic food webs and provides
the basis for the creation of vegetation cover and soils and their associated carbon
stocks. NPP is one of the most important indicators of ecosystem capacity and
forms the basis for the existence of all biodiversity (Vitousek et al. 1986; Wright
1990).
Insofar as humans use land for their purposes, they intervene in these processes.
First, they replace natural ecosystems, such as forests and grasslands, with ecosystems
utilized by humans, such as settlement areas, agricultural ecosystems and
managed forests (possibly causing soil degradation in the process). The NPP of
the ecosystems thus utilized often differs significantly from that of natural ecosystems.
The difference between the NPP of potential natural vegetation (NPPpot,
NPP of the ecosystem with no human influence) and the vegetation that is predominant
due to the land use at a particular point in time (NPPact, actual NPP) is
defined as HANPPluc (HANPP resulting from land use). Added to this—and this
is, in many instances, the actual purpose of land use—is the harvest of biomass for
6Exceptions include raised bogs, which are able to create long-term carbon sinks because of the
exclusion of oxygen in the soil.
willi.haas@aau.at
333Method Précis: Human Appropriation of Net Primary Production (HANPP)
human use (HANPPharv, HANPP through harvest). In the current definition, which
underpins the research presented in this book (see Haberl et al. 2007, 2014; the
notation used here was taken from Krausmann et al. 2013, yet the concept remains
the same), HANPPharv is relatively broadly defined and includes those parts of
plants that, although they are not themselves economically utilized and actually
removed, die off during the harvest. These include, for example, the roots of cereal
crops and trees (by contrast, the rootstocks of perennial grasses survive the harvest
and are therefore not included in calculations) and the harvest of by-products
that remain on the field. In contrast to HANPPharv, which is always greater
than or equal to zero, HANPPluc can also be less than zero. This is the case when
land use increases NPP, which is a common occurrence where artificial irrigation
is employed in agriculture. However, land use can also increase NPP in humid
regions, for example, in very intensively used agricultural regions. Nonetheless,
the NPPact of agricultural ecosystems is often smaller than the NPPpot. The primary
purpose of agriculture is to favor the cultivation of plants that produce
a greater quantity of plant matter that can be utilized for human food, livestock
feed or other economic purposes than natural vegetation would. Examples of
usable plant matter are cereal grains and hay rather than unusable leaves or roots.
Agriculture is primarily interested in an increase in the economically valuable
parts of plants. Whether the NPP of the system rises or falls in the process is not
per se important in economic terms but only inasmuch as this produces an increase
in the desired harvest. HANPP can therefore be defined as follows (Haberl et al.
2007, 2014):
HANPPluc
HANPPharv
NPPeco
Actual
vegetation
Potential
vegetation
NPPpot
HANPP
NPP[kg/aorkgC/aorJ/a]
Societal perspective: HANPP = HANPP plus HANPP
(i.e., effect of harvest and land conversion)
Ecological perspective: HANPP = NPP minus HANPP
(i.e., impact on energy availability)
luc harv
pot harv
NPPact
Fig. 14.5 The concept of the human appropriation of net primary production (HANPP)
willi.haas@aau.at
334 H. Haberl
If one subtracts the HANPPharv from the NPPact, the result is the amount of NPP
remaining in the ecosystem after harvest (and thus available to fulfill the ecosystem
functions described above, i.e., the food required by heterotrophic organisms
or the production/maintenance of carbon stocks). This is defined as NPPeco (NPP
remaining in the ecosystem). An equivalent definition of HANPP is, therefore
(Fig. 14.5),
HANPP can be positive or negative, although a negative HANPP
(NPPeco > NPPpot), as a rule, only occurs in arid areas with a low NPPpot, which
must be irrigated for agricultural purposes. In other words, HANPP is negative
when HANPPluc is negative and the absolute value of HANPPluc is greater than
HANPPharv. This occurs in arid areas, not in humid regions where intensive agriculture
is practiced.
In the literature, other definitions of HANPP are sometimes used, particularly
the formulation of Vitousek et al. (1986). The definition used here is a further
development of the definition produced by Wright (1990). The influential study
by Imhoff et al. (2004) used a consumption-based approach similar to ‘embodied
HANPP’ (Chap. 16). As shown by Haberl et al. (2007), the results of HANPP calculations
vary significantly according to the definition used. It is thus of decisive
importance that the particular definition used be taken into consideration when
interpreting HANPP data.
(14.1)HANPP := HANPPluc + HANPPharv.
(14.2)HANPP := NPPpot − NPPeco.
References
Haberl, H., Erb, K.-H., Krausmann, F., Gaube, V., Bondeau, A., Plutzar, C., et al. (2007).
Quantifying and mapping the human appropriation of net primary production in earth’s terrestrial
ecosystems. Proceedings of the National Academy of Sciences, 1 04, 12942–12947.
Haberl, H., Erb, K.-H., & Krausmann, F. (2014). Human appropriation of net primary production:
Patterns, trends, and planetary boundaries. Annual Review of Environment and
Resources, 39, 363–391.
Imhoff, M. L., Bounoua, L., Ricketts, T., Loucks, C., Harriss, R., & Lawrence, W. T. (2004).
Global patterns in human consumption of net primary production. Nature, 429, 870–873.
Körner, C. (2009). Biologische Kohlenstoffsenken: Umsatz und Kapital nicht verwechseln
(Biological carbon sinks: Turnover must not be confused with capital). Gaia—Ecological
Perspectives for Science and Society, 1 8, 288–293.
Krausmann, F., Erb, K.-H., Gingrich, S., Haberl, H., Bondeau, A., Gaube, V., et al. (2013).
Global human appropriation of net primary production doubled in the 20th century.
Proceedings of the National Academy of Sciences, 1 1 0, 10324–10329.
Vitousek, P. M., Ehrlich, P. R., Ehrlich, A. H., & Matson, P. A. (1986). Human appropriation of
the products of photosynthesis. BioScience, 36, 363–373.
Wright, D. H. (1990). Human impacts on energy flow through natural ecosystems, and implications
for species endangerment. Ambio, 1 9, 189–194.
willi.haas@aau.at