Instalaciones que cumplen con el artículo 4

In earlier studies, resource burn-off rates were investigated (Ragnarsdottir, 2008; Ragnarsdottir et al., 2011). These studies are based on quantifying the resource over quantity used per year (with some indications of recycling). Even though this is rather simplistic, it can serve as a useful indicator of how far resources can last into the future. We then analysed the world resource system and focused the study on phosphorus, people and society based on system dynamics (Sverdrup and Ragnarsdottir, 2011). Hubbert’s curves for phosphorus and systems analysis outputs are given in Figures 5.2-5.3 and outputs from the system dynamics model FoF in Figure 5.5. The figures show that peak phosphorus is upon us and we need to bear this in mind when thinking about food security and population, because the mined phosphorus is largely turned into fertiliser for food production. Our aim was to understand sustainability constraints to help decision-makers plan for a future. We addressed the following research questions:

1. How long will the world’s phosphorus supply last under the present rate of use and recycling paradigm?

2. How much can the supply be extended in terms of time and population size by enhanced recycling of all kinds?

3. How large a population can we supply with food for 10,000 years with the available phosphorus resources?

In our previous study we adopted a long-term perspective, where the short- term perspective is the time period of 1900-3600 AD (1,700 years), and the long- term perspective is the time until the next glaciation, approximately 10,000 years from now. We illustrate our case with the phosphorus cycle and the human population, modelled on a global scale with a simple model.

We did not address the following issues in this work in any detail: • The availability of agricultural soils, loss of arable land due to soil

erosion, loss of agricultural land to encroachment, soil salinisation etc. It is known that soil erosion is much faster than soil formation (Brantley

et al., 2007).

• The effect of climate change on agricultural soils, effects of drought, increased temperatures on growth of crops, water shortages and new soils becoming available further north.

• Future technical miracles that would save us from all problems. • Pollution, pesticide soil damage or chemical spill damage to soils. • Effects of limitation in energy in the future on food production. • Effect of soil sealing due to city and road construction.

Despite these clear limitations, we made estimates and subsequently discuss them in the light of these assumptions.

Figure 5.1 The food system is linked to resources through phosphorus extractable amounts and fossil fuels, as well as metals. Soils are also a very important, non-renewable resource. R is reinforcing loop, B is a balancing loop.

Figures 5.2-5.3 show that not only are we at peak phosphorus, but we are also at a time of peak tilled soils according to our Hubbert´s analysis of soil data from FAO (2010, 2011) (Fig. 2.1). It is therefore imperative not only to study the peak production behaviour of phosphorus for food security in the future, but also to link that to the population carrying capacity of the Earth. Applying the Hubbert’s model to soil data, assumes that we are mining a resource where the mining rate exceeds the regeneration rate. The Hubbert’s model fits the data well, suggesting that we may view our soil resource to be undergoing mining through erosion. As is apparent from the curve (the peak soil figure shown in Fig. 2.1), the soil resource peaked in 2005. We should interpret this as a diagnostic indicator; that there is something very unsustainable in how we are at present managing soils as a resource. This could potentially be the single largest identified threat to the general survival of civilisation on the planet because soils form very slowly (of the order of 10 mm per 100 years; Brantley et al., 2007). Without soils there will be no way to feed the population. This augments the gravity of the situation created by peak phosphorus.

5.3 Methods

The main resource prerequisites for food production aside from land and water are phosphorus and nitrogen as is illustrated in Figure 5.1. These two rely heavily on fossil deposits of phosphorus rock and oil (for hydrogen to capture nitrogen from the atmosphere). Animals play an important role in providing phosphorus and nitrogen to the nutrient chain. It is evident that with increased population, the consumption of phosphate rock increases, which in turn increases produc- tion. Increasing consumption and population are the two major factors for an increasing demand for phosphorus in the world. Recycling represents a way to increase phosphorus in the cycle without depleting resources. Thus in the world of limited resources this becomes a strategic management tool. Environmental degradation and declining resources have an effect on political and public aware- ness. Penck (1925), based on the work of von Liebig et al. (1841) and von Liebig (1843), defined the basic equation for the number of people that can be fed, the maximum population, called “Liebig’s law”:

Sustainable population = Total resource available annually/

Individual annual consumption (5.1) The equation is applied if the resource is renewable. If it is neither renewable nor substitutable, but constitutes a one-time heritage, then the annual sustainability estimate is:

Total resource available annually = Total resource volume/

Time to doomsday (5.2) The time to doomsday is estimated as the time to the end of our consideration, potentially the time of eclipse of human civilisation (Bech Nielsen, 1989; Gott III, 1994; Leslie, 1998, Sowers, 2002; Sober, 2003; and the other alternatives of Hubbert 1956, 1982). We have to remember that the individual consumption is not the individual physiological requirement, and it includes all the efficiencies from the first extraction from the deposit, until it reaches the individual consumer.

Supply = Extracted amount * Product of all efficiencies

in the supply chain (5.3) The extraction steps may be many and the inefficiencies may add up. The carrying capacity of the Earth under total sustainability will be a sustainable population number:

Sustainable population = mini {SustPopi} (5.4)

Where SustPopi is the sustainable population estimate for limiting factor i. i may

be based on phosphorus, nitrogen, water, soil, oil etc. Figure 5.3 depicts the supply of phosphorus over demand for a best-case scenario (a) and worst case scenario from a model study reported by Mohr and Evans (2013). The model projections were created by running a flow sheet model of supply against demand. Of note is that their shape is similar to our Hubbert’s curves for phosphorus production (Fig.5.2) from 2011, indicating that both methods are pointing towards scarcity

in the not so distant future. Note the consistency between Figures 5.2 and 5.3, deriving from two independent assessments, suggesting that we identified a significant issue.Where estimates represent the different aspects that can limit growth (nitrogen, phosphorus, water, light, essential elements, soil substrate availability). Many studies have considered these one by one, a few have done several, but none have done them all.

Table 5.1 Input data for URR to the integrated phosphorus supply model assessment. Major global phosphate extractable amounts (adapted from Ehrlich et al., 1992; Smil, 2001; Filippelli, 2008; USGS 2008), and scaled for use in the model. Deposit type Phosphate rock, tonnes Availability

High grade deposits 16,000 million High grade Low grade deposits 25,000 million Low grade Ultra low grade deposits 50,000 million Ultra low grade

Sum known amounts (1800) 93,000 million

Hidden high grade 1800 4,000 million High grade Hidden low grade 1800 20,000 million Low grade Hidden ultralow grade 1800 50,000 million Ultra low grade

Sum unknown amounts (1800) 74,000 million

Stored in soils of all kinds 200,000 million Available for plants only

a b

Figure 5.2 Hubbert’s curves, using our 2011 available reserve estimates (a), but eliminating resources that are contaminated or technically out of reach (URR = 19 billion tonne phosphate rock). The different curves reflect different types of deposits, in broad terms as high grade, low grade and ultralow grade amounts. The Y axis has tonne per year phosphate rock in (a). (b) Shows the output from the WORLD model, using estimates of URR of 31 billion tonne phosphate rock (small reserve) and 62 billion tonne phosphate rock (big reserve). Soil resources as 200 billion tonne phosphate rock equivalent comes in addition. The X axis in both plots are calendar year.

a

b

Figure 5.3 Two phosphorus supply projections created by running a flow sheet model of supply against demand. (a) The best case and (b) The low demand case. In either case the phosphorus supply is limited (Jasinski, 2006; Mohr and Evans, 2013). Each plot shows in million metric tonne phosphorus per year. Our study falls in between these predictions.