Human Appropriation of Net Primary Production (HANPP)
Trends and patterns of land resource use
Human Appropriation of Net Primary Productivity (HANPP) is the proportion of terrestrial NPP consumed directly and indirectly through human land use. Hence, HANPP can serve as an integrated measure of the socioecological impact of human land-use change.
HANPP describes the partitioning of NPP at the point where human land use takes place. Complementary HANPP approaches consider the human demand of NPP at the place of consumption and involve integration of population and biomass trade data. The ‘embodied HANPP’ aims to address the spatial disconnect between biomass production and consumption to characterise associated socio-economic and environmental telecoupling.
Global patterns and trends of HANPP
Spatial and temporal patterns of HANPP and its components reveal regional differences in the interactions between socioeconomic and ecological systems that may also be relevant to land degradation. Converting an undisturbed ecosystem into croplands, managed forests or tree plantations, infrastructure and built-up area tends to reduce NPP. For example, when a forest is replaced by a built-up area, the actual NPP is greatly reduced compared to its potential. Agro-ecosystems are generally less productive in terms of NPP than the natural vegetation they replace. However, in drylands, the NPP of irrigated croplands will likely exceed that of potential vegetation (i.e. NPP_act > NPP_0). The global map here represents the change in potential NPP due to human land transformation. It indicates where and the degree to which the original primary production has been modified as a result of current land use. The six combined bar and line charts associated with the main map illustrate the temporal development of HANPP components, roughly showing three global patterns:
- Regions where ecosystem change resulted in a high loss of natural capacity to provide NPP tend to have HANPP_LC values greater than 30 % (dark yellow to reddish colours). In many cases this is related to low-input agriculture with modest levels of NPP harvested for human use. These tend to be areas with “yield gaps” especially in sub-Saharan Africa, south-eastern Europe, central Asia and, to a lesser extent, in parts of southern and South-East Asia. In industrial agriculture regions, initially high values of HANPP_LC may eventually be offset through high inputs that increase crop yields and raise actual NPP to levels closer to potential NPP. In any case, land conversion combined with high inputs can place great pressures on land and water resources, ecosystem services and biodiversity. This situation is found mainly in North America, the European Union, Australia, parts of China and Asian countries with industrial economies.
- Areas with moderately negative values of NPP-LC occur where human land use has driven actual NPP above potential NPP. This is found in developed industrial regions with high input, efficient agriculture, and generally favourable environmental conditions in parts of the European Union, parts of China and South Korea.
- The highest negative values occur in dryland areas with low potential NPP. Here, almost all agricultural production is fully dependent on irrigation and fertiliser use. These inputs allow for the production of actual NPP that far exceeds potential NPP. Prominent examples are the Nile delta, the Indus Valley and the Arabian Peninsula.
Meaningful interpretations cannot be made from single date HANPP_LC estimates. Other elements of the HANPP framework are helpful. In particular the synoptic view on the relationship between the biomass extracted for human use (NPP_h) and NPP_LC and total HANPP helps distinguish other regional HANNP patterns and interpretation of combined land use intensity and efficiency. The graph ("Time series 1910- 2005 of continental HANPP") summarises global and continental trends of HANPP. Between 1910 and 2005, human population has quadrupled and overall economic production (GDP) has grown by a factor of 17, although global HANPP only doubled from 13 % to 25 % of potential terrestrial NPP1. The increase in demand for biomass that might be expected from this growth was partly offset by agricultural expansion, but mostly by increases in agricultural efficiency. Increased efficiency (through increased inputs) increased the NPP of agricultural land, in many cases to close or even beyond potential NPP. The adjacent graph ("Time series 1910-2005 continental NPP_lc/NPP_harvest") illustrates the temporal development of the ratio between NPP lost to land use change (HANPP_LC) versus the NPP actually harvested for human consumption. This ratio declines with increasing land use efficiency and has decreased globally by 50 %. This systematic decline begins in the 1950s and 1960s and generally coincides with the mechanisation of agriculture after 1945 and the subsequent green revolution in the 1960s that introduced new and high productivity crops worldwide. Nevertheless, globally, there are substantial regional differences in the evolution of HANPP and its components over the past 100 years. These reflect different socio-environmental pathways at continental scales.
Africa has increased HANPP almost 3-fold (7 % to 20 % of potential NPP). However, HANPP_LC has increased with the same order of magnitude as the HANPP_h (harvested NPP). The 1:1 relationship between HANPP_LC and HANPP_h in 2005 is an indication of land-use inefficiency.
Latin America and the Caribbean show significant increases in HANPP (from 5 % to 17 % of potential NPP). HANPP_LC increased and gains in HANPP_h show only a moderate increase in land use efficiency with a portion of HANPP_LC above the global average.
Asia doubled HANPP from 20 % to 40 % of potential NPP and has thus succeeded in largely satisfying the rapidly increasing demand of its growing population. Notably, HANPP_LC has steadily declined while HANPP_h has more than doubled. Currently HANPP_h exceeds HANPP_LC by a factor of 5, which strongly suggests a significant gain in land-use efficiency.
The highly industrialised part of the globe is composed of western and central Europe, North America, Australia and New Zealand, Japan and South Korea. They have no common geographical connection but are characterised by highly industrialised economies and efficient landuse systems that were largely established or consolidated during the last century. Since the middle of the last century, HANPP has increased only modestly (from 18 % to 23 % of potential NPP) and remained generally stable. Embedded within this general pattern are many sub-regions which deviate from regional averages. For example, a detailed study of European Union countries revealed that total HANPP is greater than 40 % and HANPP_LC remains distinctly above average due to the high density of built-up areas and infrastructure in central Europe.
The territory of the Former Soviet Union and Eastern Europe (FSU-EE) is the only region that has shown a decline in HANPP over the observed period. Up to 1990 it followed a similar pathway and level of total HANPP as the highly industrialised parts of the globe. But after 1990, the region experienced a distinct decline of HANPP due to the political and economic disruption that followed the collapse of the FSU.
HANPP and land degradation
Global patterns and trends of HANNP reflect global resource exploitation, pressures on ecosystem services and the ultimate limits to sustaining life on Earth (planetary boundaries). The application of the HANPP framework is scale-independent and its ability to suggest multiple global change issues that highlight areas of concern complements the underlying concept of ‘convergence of evidence’ proposed in this atlas.
Land degradation processes are often triggered by land conversions and the concept of HANPP_LC is one measure that can be employed to identify areas of potential risk. Soil degradation can accompany high values of HANPP_LC even as actual NPP declines. Over the long term, it was estimated that 4 to 10 % of potential NPP lost in drylands could be due to soil degradation. Alternatively, the Economics of Land Degradation initiative (ELD) used the ratio of actual NPP versus potential NPP as a spatially explicit proxy factor of land degradation. This was combined with a layer of ecosystem values (monetary values of ecosystem services for land-cover types) to estimate the cost of land degradation in the NPP supply area.
However, interpreting HANPP components alone as an indicator of potential land degradation may also be misleading. For example, high-input agriculture can increase actual NPP to levels that are comparable to potential NPP. This would mask the potentially adverse impacts of excess inputs on longterm soil and water quality and general ecosystem functioning. While a useful measure, in the absence of context, HANPP alone may not always be a reliable indicator of potential degradation.
Global HANPP estimates are based on a combination of vegetation modelling, land use and productivity statistics (e.g. agricultural and forestry yield, livestock density, other biomass flows associated with land use, etc.), global land-cover/land-use data as well as actual NPP figures
that are primarily derived from satellite imagery. Many inputs, such as time series from national to global scales, are increasingly available. The main components for estimating HANPP are:
NPP_0: is derived from bio-climatic models and refers to the potential vegetation that would prevail in a defined area under current
soil and climate conditions without human intervention.
NPP_act: is the NPP of the actual production under current land use, which can be derived from global satellite data.
NPP_h: is the NPP that is harvested (e.g. in agricultural yields, timber production and other biomass products) compiled from statistical databases which are spatially disaggregated.
NPP_t: is the NPP remaining in the ecosystem after human harvesting
From these components the following can be derived:
HANPP_LC = NPP_0 – NPP_act (accounts for the NPP change due to human land-use conversion)
NPP_t = NPP_act – NPP_h (accounts for the NPP remaining in the ecosystem after harvesting – also called NPP_eco
HANPP = NPP_h + NPP_LC= NPP_0 – NPP_t
Source: WAD3-JRC, 2018; derived from: Haberl, H., 2014, Plutzar, C., 2016, Kraussmann, F., 2013, 2012..
Source: WAD3-JRC, 2018; derived from: Haberl, H., 2014, Plutzar, C., 2016, Kraussmann, F., 2013, 2012..