Louise Karlberg

A safe operating space for humanity

Identifying and quantifying planetary boundaries that must not be transgressed could help prevent human activities from causing unacceptable environmental change, argue Johan Rockstrom and colleagues.

Future water availability for global food production: The potential of green water for increasing resilience to global change

Future water availability for global food production : the potential of green water for increasing resilience to global change

Present and future water requirements for feeding humanity.

The Comprehensive Assessment of Water Management in Agriculture recommended that future food production should be concentrated on existing agricultural land in order to avoid further loss of ecosystem functions from terrestrial lands. This paper is a green-blue water analysis of water constraints and opportunities for global food production on current croplands (including permanent pasture). It assesses, for the target year 2050, (1) how far improved land and water management would go towards achieving global food security, (2) the water deficits that would remain in water scarce regions aiming at food self-sufficiency, (3) how those water deficits may be met by food imports, (4) the cropland expansion required in low income countries without the needed purchasing power for such imports, and (5) the proportion of that expansion pressure which will remain unresolved due to potential lack of accessible land. The water surplus remaining on current cropland is compared with water requirements for biofuel production as a competing activity.

The quadruple squeeze : defining the safe operating space for freshwater use to achieve a triply green revolution in the Anthropocene

Humanity has entered a new phase of sustainability challenges, the Anthropocene, in which human development has reached a scale where it affects vital planetary processes. Under the pressure from a quadruple squeeze—from population and development pressures, the anthropogenic climate crisis, the anthropogenic ecosystem crisis, and the risk of deleterious tipping points in the Earth system—the degrees of freedom for sustainable human exploitation of planet Earth are severely restrained. It is in this reality that a new green revolution in world food production needs to occur, to attain food security and human development over the coming decades. Global freshwater resources are, and will increasingly be, a fundamental limiting factor in feeding the world. Current water vulnerabilities in the regions in most need of large agricultural productivity improvements are projected to increase under the pressure from global environmental change. The sustainability challenge for world agriculture has to be set within the new global sustainability context. We present new proposed sustainability criteria for world agriculture, where world food production systems are transformed in order to allow humanity to stay within the safe operating space of planetary boundaries. In order to secure global resilience and thereby raise the chances of planet Earth to remain in the current desired state, conducive for human development on the long-term, these planetary boundaries need to be respected. This calls for a triply green revolution, which not only more than doubles food production in many regions of the world, but which also is environmentally sustainable, and invests in the untapped opportunities to use green water in rainfed agriculture as a key source of future productivity enhancement. To achieve such a global transformation of agriculture, there is a need for more innovative options for water interventions at the landscape scale, accounting for both green and blue water, as well as a new focus on cross-scale interactions, feed-backs and risks for unwanted regime shifts in the agro-ecological landscape.

Modeling Carbon Turnover in Five Terrestrial Ecosystems in the Boreal Zone Using Multiple Criteria of Acceptance

Abstract Estimates of carbon fluxes and turnover in ecosystems are key elements in the understanding of climate change and in predicting the accumulation of trace elements in the biosphere. In this paper we present estimates of carbon fluxes and turnover times for five terrestrial ecosystems using a modeling approach. Multiple criteria of acceptance were used to parameterize the model, thus incorporating large amounts of multi-faceted empirical data in the simulations in a standardized manner. Mean turnover times of carbon were found to be rather similar between systems with a few exceptions, even though the size of both the pools and the fluxes varied substantially. Depending on the route of the carbon through the ecosystem, turnover times varied from less than one year to more than one hundred, which may be of importance when considering trace element transport and retention. The parameterization method was useful both in the estimation of unknown parameters, and to identify variability in carbon turnover in the selected ecosystems.

Assessing the implications of water harvesting intensification on upstream–downstream ecosystem services: A case study in the Lake Tana basin

Water harvesting systems have improved productivity in various regions in sub-Saharan Africa. Similarly, they can help retain water in landscapes, build resilience against droughts and dry spells, and thereby contribute to sustainable agricultural intensification. However, there is no strong empirical evidence that shows the effects of intensification of water harvesting on upstream-downstream social-ecological systems at a landscape scale. In this paper we develop a decision support system (DSS) for locating and sizing water harvesting ponds in a hydrological model, which enables assessments of water harvesting intensification on upstream-downstream ecosystem services in meso-scale watersheds. The DSS was used with the Soil and Water Assessment Tool (SWAT) for a case-study area located in the Lake Tana basin, Ethiopia. We found that supplementary irrigation in combination with nutrient application increased simulated teff (Eragrostis tef, staple crop in Ethiopia) production up to three times, compared to the current practice. Moreover, after supplemental irrigation of teff, the excess water was used for dry season onion production of 7.66 t/ha (median). Water harvesting, therefore, can play an important role in increasing local- to regional-scale food security through increased and more stable food production and generation of extra income from the sale of cash crops. The annual total irrigation water consumption was ~4%-30% of the annual water yield from the entire watershed. In general, water harvesting resulted in a reduction in peak flows and an increase in low flows. Water harvesting substantially reduced sediment yield leaving the watershed. The beneficiaries of water harvesting ponds may benefit from increases in agricultural production. The downstream social-ecological systems may benefit from reduced food prices, reduced flooding damages, and reduced sediment influxes, as well as enhancements in low flows and water quality. The benefits of water harvesting warrant economic feasibility studies and detailed analyses of its ecological impacts.

Global food production in a water-constrained world : exploring ‘green’ and ‘blue’ challenges and solutions

Global food production in a water-constrained world : exploring ‘green’ and ‘blue’ challenges and solutions

Can rainfed agriculture feed the world?: an assessment of potentials and risk

Agriculture is practised on 12% of the total land area, hosting around 42% of the global population (FAOSTAT, 2000, 2003). Most of this area, around 80%, is under rainfed agriculture (FAOSTAT, 2005), which plays a predominant role in global food supply and water demand for food. There are large regional variations. While the majority of the agricultural land in sub-Saharan Africa is rainfed, most of the agricultural production in South Asia comes from irrigated agriculture. Approximately 7000 km3 of water is used annually in crop production (Rockström et al., 1999; de Fraiture et al., 2007; Lundqvist et al., 2007), corresponding to 3000 l/person/day. The majority of this water originates from the green water resource (78%), while the remaining 22% is met by irrigation (de Fraiture et al., 2007). Today, more than 1.2 billion people live in water-scarce river basins (Molden et al., 2007a), and recent forecasts warn of aggravated global water scarcity unless water resources management is changed (Alcamo et al., 1997; Seckler et al., 1998; Seckler and Amarasinghe, 2000; Shiklomanov, 2000; Rosegrant et al., 2002a, 2006; Bruinsma, 2003; Falkenmark and Rockström, 2004; SEI, 2005). With rising incomes and growing population, food demand is expected to increase by 70–90% (de Fraiture et al., 2007). Food habits change with increasing GDP (gross domestic product) to include more nutritious and more diversified diets, resulting in a shift in consumption patterns among cereal crops and away from cereals towards livestock products and high-value crops such as fruits, vegetables, sugar and edible oils; however, regional and cultural differences are large. Bioenergy is expected to add to the demand of agricultural produce, in order to increase the supply of transport fuels (i.e. biofuels) as a response to rising energy prices, geopolitics and concerns over greenhouse gas emissions. Future water requirements for bioenergy production have been estimated to range from 4000 to 12,000 km3/year (Lundqvist et al., 2007). The large uncertainty is a reflection of difficulties in estimating water productivity, which, for example, depends on how much of the biomass can be used for bioenergy production. One of the options to respond to increased pressure on water resources is to boost low productivity through investments in water management in rainfed agriculture. There are several compelling environmental, social and economic reasons to do so. Yet, with rapidly growing and changing agricultural demand and increased climate variability due to climate change, the potential of rainfed agriculture to meet future food demand is subject to debate.

Towards more spatially explicit assessments of virtual water flows: Linking local water use and scarcity to global demand of Brazilian farming commodities

Global consumption of farming commodities is an important driver of water demand in regions of production. This is the case in Brazil, which has emerged as one of the main producers of globally traded farming commodities. Traditional methods to assess environmental implications of this demand rely on international trade material flows at country resolution; we argue for the need of finer scales that capture spatial heterogeneity in environmental variables in the regions of production, and that account for differential sourcing within the borders of a country of production. To illustrate this, we obtain virtual water flows from Brazilian municipalities to countries of consumption, by allocating high-resolution water footprints of sugarcane and soy production to spatially-explicit material trade flows. We found that this approach results in differences of virtual water use estimations of over 20% when compared to approaches that disregard spatial heterogeneity in sourcing patterns, for three of the main consumers of the analysed crops. This discrepancy against methods using national resolution in trade flows is determined by national heterogeneity in water resources, and differential sourcing. To illustrate the practical implications of this approach, we relate virtual water flows to water stress, identifying where global demand for water coincides with high levels of water stress. For instance, the virtual water flows for Brazilian sugarcane sourced by China were disproportionally less associated to areas with higher water stress when compared to those of the EU, due to EUs much higher reliance on sugarcane from water scarce areas in Northeast Brazil. Our findings indicate that the policy relevance of current assessments of virtual water flows that rely on trade data aggregated at the national level may be hampered, as they do not capture the spatial heterogeneity in water resources, water use and water management options.

Water resource implications of upgrading rainfed agriculture – focus on green and blue water trade-offs

Water resource implications of upgrading rainfed agriculture – focus on green and blue water trade-offs