Feeding Ten Billion People Is Possible Within Four Terrestrial Planetary Boundaries

Global agriculture puts heavy pressure on planetary boundaries, posing the challenge to achieve future food security without compromising Earth system resilience. On the basis of process-detailed, spatially explicit representation of four interlinked planetary boundaries (biosphere integrity, land-system change, freshwater use, nitrogen flows) and agricultural systems in an internally consistent model framework, we here show that almost half of current global food production depends on planetary boundary transgressions. Hotspot regions, mainly in Asia, even face simultaneous transgression of multiple underlying local boundaries. If these boundaries were strictly respected, the present food system could provide a balanced diet (2,355 kcal per capita per day) for 3.4 billion people only. However, as we also demonstrate, transformation towards more sustainable production and consumption patterns could support 10.2 billion people within the planetary boundaries analysed. Key prerequisites are spatially redistributed cropland, improved water–nutrient management, food waste reduction and dietary changes.

Adoption of the Sustainable Development Goals by all nations
in 2015 is the first ever commitment to a world development
path that safeguards the stability of the Earth system
as a prerequisite for meeting universal human standards1. The longstanding
challenge of achieving food security through sustainable
agriculture is particularly acute in this context as world agriculture
is a leading cause for the current transgressions of multiple planetary
boundaries (PBs) globally and regionally2–5. The PB framework
is a comprehensive scientific attempt to synoptically define
our planet’s biogeophysical limits to anthropogenic interference. It
suggests bounds to nine interacting processes that together delineate
a Holocene-like Earth system state. The Holocene is chosen as
the reference state as it is the only period known to provide a safe
operating space for a world population of several billion people,
and according to a precautionary principle, the PBs are set in sufficient
distance from processes that may critically undermine Earth
system resilience and global sustainability. A challenging question,
thus, is whether human development goals such as food security
can be met while maintaining multiple PBs along with their subglobal
manifestations.
Further PB transgressions could jeopardize the chances of providing
sufficient food for a world population projected to be wealthier
and reach >9 billion by 2050. This conundrum portrays a tradeoff
between Earth’s biophysical carrying capacity and humankind’s rising
food demand, calling in response for radical rethinking of food
production and consumption patterns6–9. Yield gap closures, avoidance
of excessive input use, shifts towards less resource-demanding
diets, food waste reductions and efficient international trade are
crucial options for sustainably increasing the food supply10–15. For
example, enhancing water-use efficiency on irrigated and rain-fed
farms can triple or quadruple crop yields in low-performing systems,
suggesting possible global gains of >20% (ref. 16). Even higher gains
appear feasible through globally optimized configurations of the
land-use pattern17, and cutting food losses by half could generate
food for another billion people18. Thus, collective large-scale implementation
of such options could sustain food for a further growing
world population19. Yet achieving this within a safe operating space
as defined by PBs requires not only a halt to but actually a reversal
of existing PB transgressions. Previous studies suggest that such a
reconciliation might be possible, but these were based on aggregate
representations of PBs (not accounting for the spatial patterns
of limits, transgressions and interactions) or considered only one
boundary in isolation17,20–23.
Here, we systematically quantify to what extent current food production
depends on local to global transgressions of the PBs for biosphere
integrity, land-system change, freshwater use and nitrogen
(N) flows, along with the potential of a range of solutions to avoid
these transgressions and still increase food supply (Table 1). To this
end, we configured an internally consistent process-based model of
the terrestrial biosphere including agriculture (LPJmL) with multiple
spatially distributed PBs and their interactions. LPJmL is among
the longest-established and best-evaluated biosphere models, showing
robust performance regarding simulation of, for example, carbon,
water and crop yield dynamics (Supplementary Figs. 1 and 2
and Supplementary Table 1; see ref. 24 for a comprehensive benchmarking
and Supplementary Methods for more detail on model
evaluations). In principle following established definitions4, we
refine the computation of some PBs with respect to their regional
patterns and interactions (Methods), providing globally gridded
precautionary limits to human interference with the Earth system at
a level of great detail. In particular, we account for the evidence that
many PBs need to be represented spatially explicitly4 to cover their