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France and the nine planetary boundaries
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Disruption of nitrogen and phosphorus biogeochemical cycles

Disrupted life cycles, leading to exceedance of global nitrogen boundaries

Nitrogen and phosphorus, essential nutrients, play a central role in plant growth. Given their strong interactions and the stakes they represent in maintaining the Earth system's natural equilibrium, scientists have chosen to consider them as a single planetary limit. Since the industrial revolution, the use of nitrogen and phosphorus by human activities, mainly for agricultural purposes, has disrupted their natural cycle. While this use has considerably increased crop yields and fed an ever-growing world population, it is not without consequences for the environment.

Nitrogen is a particularly abundant gas in the atmosphere (78% by volume). Through a succession of natural processes, it is transformed into ammonium or nitrate. This is known as "reactive nitrogen" (see glossary), and can be directly assimilated by plants. Since the beginning of the twentieth century, this natural cycle has been disrupted by the appearance of industrial processes producing reactive nitrogen, and in some places by the density of intensive livestock operations producing nitrogen effluents in excess of what can be absorbed by arable land. Large quantities of fertilizers and nitrogen effluents are thus produced and used intensively in agriculture, and end up in the environment (surface and groundwater in particular).

Phosphorus is a rare element on the Earth's surface. It is mainly stored as phosphate in water, soil, rocks and sediments. Phosphorus from the mining industry is used to produce mainly fertilizers, but also detergents. Since the 19th century, large quantities of phosphorus have been mobilized to increase agricultural productivity, thus contributing to an imbalance in the natural phosphorus cycle.

To address these issues, the authors of the planetary boundaries have taken as their control variable the "quantity of reactive nitrogen released each year into nature by human activities", on a global scale (table 4). In the case of phosphorus, they defined a two-level approach to better take into account local issues, with two geographical thresholds:

  • on a global scale, this is the annual quantity of phosphorus emitted by freshwater systems into the ocean;
  • on a regional scale, this is the annual quantity of phosphorus resulting from excessive inputs during fertilization of agricultural soils (Steffen et al., 2015).

Table 4: Control variables and planetary boundary for disruption of nitrogen and phosphorus biogeochemical cycles

Nutrients

Control variables

Thresholds and areas of uncertainty

Global values

Nitrogen

Quantity of reactive nitrogen released by human activities in millions of tonnes (Mt), per year, worldwide

62Mt per year (62-82Mt per year, or 41-55 kg/year per hectare of cultivated area)

150 Mt

Phosphorus

Global scale: quantity of phosphorus emitted by freshwater systems to the oceans, in Mt per year

11Mt per year (11-100Mt per year, or 1.5-13.5kg/year percapita20

22 Mt

Regional scale: quantity of phosphorus in fertilizers applied to agricultural soils, in Mt per year

6.2Mt per year (6.2- 11.2Mt per year, or 4.1-7.5kg/year per hectare of cultivated area)

14.2 Mt

Source: based on Steffen et al., 2015

20 World population 2015: 7.4 billion. Global cultivated area (average since 1970): 1.496 billion hectares.

The values presented above show that the planetary boundary for nitrogen has been exceeded: the quantity of reactive nitrogen released into the environment by human activities worldwide (150 Mt/year) is well above the set thresholds (62-82 Mt/year). With regard to phosphorus, worldwide flows from freshwater systems to the ocean (22 Mt) exceed the low end of the uncertainty zone (11 Mt), while remaining below the high end (100 Mt). However, on a continental scale, the quantities of phosphorus fertilizers applied to soils exceed the high value of the uncertainty zone (14.2 Mt instead of 11.2 Mt).

Consequences and challenges of agricultural uses

The massive use of nitrogen and phosphorus in fertilizers can have a series of deleterious effects on the environment. Nitrates are produced by bacteria in the presence of oxygen, and can leach into and pollute groundwater and surface water. This leaching can also lead to a surplus of nitrates in continental waters, generating plant proliferation (green algae). This phenomenon is known as eutrophication (see glossary).

The use of mineral fertilizers derived from phosphate rock can lead to excess phosphorus in freshwater. Excess phosphorus also contributes to the phenomenon of eutrophication, which leads to a deterioration in water quality, an accumulation of phosphorus in sediments and a loss of biodiversity. What's more, phosphorus discharged from freshwater systems into the oceans can lead in the very long term to a reduction in dissolved oxygen (ocean anoxia). The challenge is to avoid the widespread occurrence of such a phenomenon, which could lead to an oceanic anoxic event, threatening a large part of ocean life.

Beyond the crucial issues of pollution of aquatic environments and oceans by nitrate and phosphorus discharges, there remains the particular problem of the available phosphorus resource. The growing use of phosphorus fertilizers requires the exploitation of phosphate mines, which could run out in around 320 years according to data from the "World Extraction-Reserves" survey (U.S. Geological Survey, 2022), while humanity depends on these fertilizers for its food security.

France's contribution to exceeding the planetary boundary

Nitrogen and phosphorus sales in France on the decline

In France, according to the Union of Fertilization Industries (Unifa), the quantity of nitrogen sold per cultivated land, i.e. arable land and permanent crops, has tended to decline over the decades. It amounts to 108 kg per hectare (kg/ha) of cultivated land for the 2019-2020 campaign, compared with 121 kg/ha for the 2010-2011 campaign and 124 kg/ha for the 2000-2001 campaign (Figure 10 ). Phosphorus sales, meanwhile, have remained stable over the last ten years, at around 10 kg/ha.

Figure 10: Change in quantities of nitrogen and phosphorus sold in France between 2000 and 2020

* Cultivated land = arable land + permanent crops excluding grassland.
Note: Unifa 2019-2020 data concern the 2019-2020 campaign and the calculation is based on 2020 farmland.
Sources: Unifa; SSP, 2022. Processing: SDES, 2023

However, the indicator of mineral fertilizer sales is not a measure of nitrogen or phosphorus surpluses likely to degrade the environment. In this case, another indicator is used: the gross nutrient balance, which aims to estimate the balance between inputs and outputs of each nutrient in the agricultural soil. The Eurostat method for estimating gross nutrient balances takes into account, on the input side: mineral and organic inputs, symbiotic nitrogen gas fixation, atmospheric deposition and input from seeds; and on the output side: withdrawals during crop harvesting, withdrawals through forage harvesting and grazing, and crop residues removed from the field. When the gross nutrient balance is positive, we speak of a "surplus".

But France's nitrogen surplus remains above the planetary boundary

In France, over the 2010-2019 period, the gross nitrogen nutrient balance averages 55 kg/ha of cultivated agricultural area, compared with 63 kg/ha for the 2000-2009 period. France thus remains above the low threshold of the planetary boundary of 41 kg/ha over the 2010 decade, and is at the high threshold of the planetary limit of 55 kg/ha set by the framework of planetary boundaries, on average over the period, exceeding it in some years (Figure 11). However, this figure gives only partial information on France's impact on this limit. Indeed, it does not take into account the surplus nitrogen generated outside France to produce agricultural goods that will be consumed in France.

In 2019, the surplus of nitrogen applied in mainland France is 1.1 million tonnes, i.e. 0.75% of the estimated surplus worldwide, while France cultivates 0.6% of the world's agricultural land.

Figure 11: Gross nitrogen nutrient balance in France, 2000-2019

*Cultivated land = arable land + permanent crops excluding grassland.
Field: mainland France.
Sources: Eurostat - data updated on March 14, 2022 and extracted on January 26, 2023; Agreste, annual agricultural statistics, 2022. Processing: SDES, 2023

France's phosphorus surplus is below the planetary boundary

Over the period 2010-2019, the gross nutrient balance in phosphorus averages 2.0 kg/ha of cultivated land, compared with 6.9 kg/ha for the period 2000-2009. Since 2009, France has therefore fallen below the low threshold of the planetary boundary of 4.1 kg/ha set by the global boundaries framework (Figure 12).

Figure 12: Gross nutrient phosphorus balance in France, 2000-2019

*Cultivated land = arable land + permanent crops excluding grassland.
Note: The negative value for 2009 is explained by lower phosphorus deliveries (-54% on the previous campaign) due to falling cereal prices combined with very high phosphorus purchase prices, which led some farmers to do without this element.
Field: metropolitan France.
Sources: Eurostat - data updated on March 14, 2022 and extracted on January 26, 2023; Agreste, Statistique agricole annuelle, 2022. Data processing: SDES, 2023

In 2015, France's phosphorus balance amounted to 27,000 tonnes (30,600 tonnes in 2019), representing a 0.2% share of the global volume, while France uses 0.6% of the world's cultivated land.

As with nitrogen, the estimation of environmental pressures is based on production (phosphorus use by crops), and does not take into account the environmental impacts of French consumption of imported goods.

Phosphorus flows discharged into the sea are declining

In 2020, 15, 800 tonnes of phosphorus were discharged into the sea in mainland France. Between 2000 and 2020, phosphorus flows to the sea fell by 57% (Figure 13). This reduction is due in particular to the improved performance of wastewater treatment plants, the ban on the use of phosphate in detergents and the increase in the number of inhabitants connected to a collective sewerage system. Based on the 2020 metropolitan population, the flow discharged into the sea is 0.23 kg/capita/year, i.e. below the global limit of 1.5 kg/capita/year.

Figure 13: Total phosphorus flows reaching the sea in France from 2000 to 2020

Scope: metropolitan territories, whose outlets correspond to maritime areas monitored under the Ospar and Medpol conventions.
Source: water information system, Naïades database and hydro bank (data extraction in June 2022).
Processing: SDES, 2022

Policies and actions to combat nitrogen and phosphorus pollution

In response to the pollution of water by nitrates from agricultural sources and the eutrophication of ecosystems, the EU introduced legislation in 1991 aimed at reducing the loss of nitrates from agricultural sources and limiting eutrophication. Known as the "nitrates" directive, it provides for the monitoring of nitrate concentrations in water, the designation of zones vulnerable to nitrate pollution from agricultural sources or to eutrophication, and the establishment of an action program, the application of which is mandatory in vulnerable zones.

The aim of this regulatory framework is to optimize the use of nitrogen fertilizers, according to the formula "the right dose, at the right time and in the right place", so as to limit nitrate leakage into groundwater and surface water (ban on spreading during certain periods, storage facilities for livestock effluents, distance from watercourses, fertilization plan, maximum dose, etc.). The 2021 Climate and Resilience Act contributes to this objective by restricting the use of synthetic fertilizers on land that is not used for agricultural purposes.

By 2021, 73% of French farmland will be classified as a vulnerable zone, corresponding to 281,000 farms. On average, mineral nitrogen inputs are twice as high in vulnerable zones as outside them (Map 2).

Map 2: Vulnerable zones in France in 2021, defined in application of the 1991 "nitrates" directive

Source: OFB, Eaufrance website, Zones vulnérables - Métropole, 2022

Since the 2000s, the Common Agricultural Policy (CAP) has increasingly taken environmental issues into account. The eco-conditionality of CAP aid makes it possible to condition aid on the implementation of practices that help avoid the release of nitrates, such as buffer strips along watercourses, minimum soil cover, or the protection of permanent grasslands. The green payment provided for in the 2015-2020 CAP has thus placed the emphasis on regional monitoring of the proportion of useful agricultural area (UAA) - (see glossary) - under grassland or permanent pasture, and the protection of so-called sensitive grassland and permanent pasture (linked to Natura 2000).

In the same way, the 2023-2027 CAP plans to reinforce the cross-compliance of aid with the aforementioned good agricultural and environmental practices. In particular, requirements relating to soil cover and the absence of bare soil are reinforced outside vulnerable areas.

France's nitrate action programs are divided into two levels. The first is the national action program (PAN), which comprises eight measures to be implemented in all vulnerable zones in order to:

  • fertilize at the right time and under the right conditions (blackout periods, effluent storage, spreading conditions);
  • limit over-fertilization (balanced fertilization, provisional fertilization documents and records of practices, maximum input boundaries for livestock effluents);
  • limit nitrogen leakage from plots (soil cover and grassed strips along courses).

The second is regional action programs (RAPs), which reinforce and complement NAP measures in vulnerable areas according to local and regional specificities.

The seventh national action program came into force on January 30, 2023. The eight measures will apply as soon as the revised RAPs come into force, and no later than January 1, 2024.

Eutrophication can also be caused by excess phosphorus in freshwater, mainly due to the use of mineral fertilizers. In the past, urban wastewater was the main source of phosphorus contamination. Following the implementation of the 1991 Urban Wastewater Directive and the ban on phosphate in household detergents since 2007, discharges have fallen sharply.

There are no general national regulations concerning phosphorus pollution of agricultural origin (IOWater, 2018). However, local regulations apply according to local issues, where problems linked to phosphorus of agricultural origin have been identified (notably in Brittany). Local regulations on agricultural phosphorus are mainly defined within the framework of the Water Development and Management Master Plan (Sdage) instituted by the 1992 Water Act. For example, the Seine-Normandie Sdage includes a provision aimed at "controlling phosphorus inputs upstream of eutrophied surface water bodies or those threatened by eutrophication".

In addition, a number of restrictive regulations help to reduce the risk of water contamination by phosphates. These include regulations governing facilities classified for environmental protection (ICPE), which define the conditions applicable to the storage and spreading of livestock effluent. This is also the case for the departmental health regulations, which can be adapted to the local context.

Excessive nitrate levels have a major impact on marine ecosystems, and several regional seas conventions are working to limit this phenomenon. For example, the International Convention for the Protection of the Marine Environment of the North-East Atlantic (Ospar) and the program for the assessment and control of marine pollution in the Mediterranean region (Medpol), which depends on the Barcelona Convention for the Mediterranean Sea, provide for the monitoring of nitrogen and phosphorus flows discharged into the sea via waterways. Although no threshold values have been set, these monitoring programs contribute to better knowledge and international awareness of this issue.

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