Target 8: Pollution

SBSTTA Review DRAFT GBO4 – Technical Document – Chapter 8 DO NOT CITE 1 Target 8: Pollution 2 3 By 2020, pollution, including from excess nutrients, has been brought to levels that are not 4 detrimental to ecosystem function and biodiversity. 5 6 7 Preface 8 9 Biodiversity is affected by numerous pollutants including heavy metals emitted by mining, 10 industry and transport, pesticides used in agricultural practice, oil spills and excess of 11 nutrients especially nitrogen (N) and phosphorus (P). Given the high importance of N and P 12 impacts on biodiversity and ecosystem services at local to global scales (Fowler et al., 2013, 13 MA, 2005), the main focus of this chapter is on the pollution from N and P. Micro pollutants, 14 e.g. oil spills, plastic debris and pesticide use, are treated briefly in the section on status and 15 trends and 2020 projections, but are not treated in subsequent sections due to the lack of 16 long term scenarios. It should also be stressed that we discuss the pollutants separately, 17 while in reality areas might suffer from multiple pollutants. 18 19 Nitrogen - There are many natural processes that generate nitrogen (N) inputs into 20 ecosystems, but industry, transport and agriculture have greatly increased N inputs (Fowler 21 et al., 2013, Sutton et al., 2013). It is the excess above natural inputs (the N surplus) that is 22 referred to as N pollution. In non-agricultural terrestrial ecosystems, N pollution primarily 23 arises from wet and dry deposition of N that has been emitted into the air by industry, 24 transport and agriculture (direct effects of N fertilizer addition to agricultural and 25 aquaculture systems are treated in Target 7). In aquatic ecosystems, N pollution comes 26 primarily from runoff and leaching of fertilizers from agricultural and to a lesser extent from 27 sewage and wet deposition. 28 29 Nitrogen pollution impacts ecosystems through a variety of mechanisms: the two most 30 important being eutrophication and acidification (Bobbink et al., 2010, Fowler et al., 2013). 31 Eutrophication is the increase in productivity and accumulation of the nutrient load in 32 ecosystems, especially by nitrogen and/or phosphorus, leading to an undesirable disturbance 33 of the balance of organisms in the ecosystem, affecting both terrestrial and aquatic 34 biodiversity (Sutton et al., 2011). Acidification of ecosystems is caused by oxidation of NOx 35 and NH3 in air, soil and water (Pardo et al., 2011). In soils nitrogen oxides, ammonia, nitrate 36 and ammonium ions can enhance the rate of acidification, where nutrient bases (calcium, 37 magnesium, and potassium) are replaced by acidic elements (hydrogen and aluminum; 38 (Sutton et al., 2011). This may lead to nutrient disorders and to toxic effects in plants (Sutton 39 & Bleeker, 2013). Because N pollution is transported in the air as gases or aerosols, 40 atmospheric N pollution can cause eutrophication and acidification in terrestrial and aquatic 41 ecosystems at substantial distances from sources of emissions. 42 43 Nitrogen accumulation is the main driver of species composition changes since many 44 species-rich terrestrial ecosystems are adapted to conditions of low N availability. In these 45 ecosystems excess of nitrogen change competitive relations, and can make conditions 46 unfavorable for some species (Bobbink et al., 2010). Other effects (e.g. direct toxicity of 47 nitrogen gases and aerosols, long-term negative effects of increased ammonium and 1 SBSTTA Review DRAFT GBO4 – Technical Document – Chapter 8 DO NOT CITE 1 ammonia availability, soil-mediated effects of acidification, secondary stress and 2 disturbances) are more ecosystem- and site-specific and often play a supporting role 3 (Bobbink et al., 2010). N pollution may also increase the dominance of invasive alien plants in 4 terrestrial ecosystems and decrease the diversity of plant communities worldwide (IAASTD, 5 2009). In addition, N emissions make an important contribution to greenhouse gas balance 6 (Butterbach-Bahl & Dannenmann, 2011). NOx emissions are a major contributor to the 7 formation of tropospheric ozone, while N2O emissions cause depletion of stratospheric 8 ozone. Tropospheric ozone has negative effects on plant productivity and human health. 9 10 Phosphorus - Phosphorus (P) has no significant atmospheric component, except for transport 11 of P attached to soil particles. Next to this, runoff from agriculture fields, sewage water from 12 households containing human excreta and detergents, and wastewater from industries are 13 the main causes of pollution. This primarily impacts aquatic ecosystems through 14 eutrophication, since P is transported more often in water and much less so in air. 15 Traditionally N pollution is thought to primarily impact non-tropical terrestrial ecosystems 16 and coastal zones, while P pollution is traditionally thought to have the largest impacts on 17 freshwater ecosystems. However, recent evidence suggests aquatic ecosystems are often 18 affected by both N and P pollution (Conley et al., 2009b, Elser et al., 2007). For example, 19 eutrophication in lakes, rivers and coastal areas caused by N and P pollution can lead to the 20 generation of oxygen depleted areas (<2 ml O2/L, hypoxia and for coastal systems also known 21 as “dead zones”), the formation of harmful algal blooms (Anderson et al., 2002), increased 22 occurrence of pathogenic microorganisms, and uncontrolled population growth of certain 23 weedy plants or gelatinous zooplankton. 24 25 To regulate N and P pollution national or trans-boundary regulations which are based on the 26 concept of “critical loads” have been developed. Critical loads are thresholds above which N 27 and P pollution has negative effects on biodiversity, ecosystem function or ecosystem 28 services. For each ecosystem type, different levels of N and P are detrimental, and critical 29 loads may therefore differ between countries. For example, critical loads for atmospheric N 30 deposition in the European Union are currently set at 5-40 kg N/ha/yr depending on 31 ecosystem type (Bobbink et al., 2010), while in the United States the critical load ranges from 32 1 kg/ha/yr to nearly 40 kg/ha/yr (Pardo et al., 2011). These thresholds are based on 33 experiments, observations and models. The use of critical loads has been questioned 34 because it is difficult to precisely determine critical loads, since they are highly system 35 specific and some systems appear to be affected even at very low loads (Payne et al., 2012). 36 37 Pesticides - pesticides cover a wide range of compounds including insecticides, fungicides, 38 herbicides, rodenticides, molluscicides and nematicides. Ideally a pesticide is lethal to the 39 targeted pests, but not to non-target species. Unfortunately, pesticides can be toxic to a host 40 of other organisms, including birds, fish, beneficial insects, and non-target plants and can be 41 lethal or may cause, among others, neurological and behavior disorders (Mitra et al., 2011). 42 Pesticides can contaminate soil, water, turf, and other vegetation and can therefore be 43 transported over great distances via air and water. Pesticides are persistent and can 44 accumulate in the food chain which can lead to risks to non-target organisms (Aktar et al., 45 2009, Mitra et al., 2011). Pesticides can also cause soil degradation when they are toxic to 46 microorganisms (Aktar et al., 2009). 47 2 SBSTTA Review DRAFT GBO4 – Technical Document – Chapter 8 DO NOT CITE 1 Micro pollutants - micro pollutants include plastics, pharmaceuticals, personal care products 2 (PCPs), steroids, hormones, surfactants, perfluorinated compounds (PFCs), various persistent 3 organic pollutants (POPs), nanomaterials and swimming pool disinfection by-products (Farre 4 et al., 2008). These are derived from diverse industrial activities, fossil fuel combustion, 5 waste disposal and many other sources (Travis & Hester, 1991). Often they enter the ocean 6 through waste-water treatment plants (Farre et al., 2008). Some toxic pollutants are natural 7 elements that become widely dispersed by human activities, as in the case of radioisotopes 8 and petrochemicals (Pirrone et al., 2010). Others are xenobiotic compounds synthesized to 9 serve as pesticides, solvents and lubricants. Those micro pollutants can be acutely or 10 chronically toxic to individual organisms or accumulate in food chains and become 11 concentrated in top predators (Persson et al., 2013). Next to this, most of these compounds 12 are long-lived once released into the environment and they are able to circulate widely in the 13 atmosphere and oceans, allowing long-distance transport to sites that are distant from any 14 known source, resulting in high concentrations of many pollutants in polar animal species 15 (e.g. Braune et al., 2005). 16 17 Chemicals – chemicals (e.g. lead, cadmium, cooper, PAHs and PCBs) are emitted via industry, 18 agriculture, households and other human activities. This results in local and diffuse 19 environmental concentrations of chemicals that vary in space and time. Consequently, this 20 leads to a variety of contaminated areas; some with diffuse concentrations of chemicals 21 while hot spots have substantial local soil contamination. This leads to a highly variable 22 exposure of, amongst others, soil biota. Thereby affecting soil biodiversity, soil functioning 23 and soil processes such as the breakdown and recycling of organic materials, nutrient cycling, 24 soil fertility, as well as the breakdown of organic contaminants (ecosystem services). 25 26 Through exposure of soil biota (acting in local soil food webs) to different local composition 27 and concentrations of the contaminant mixture biodiversity is affected. Ecotoxicity effects are 28 expected to affect ecosystem function and soil biodiversity at different impact levels. For 29 large diffusely contaminated areas, the impact on soil biota originates from relatively low 30 concentrations of rather complex mixtures of contaminants over wide areas. Hotspots with 31 contamination have high enough concentrations of the mixture of contaminants to impact 32 large parts of the local soil biota in the soil food web.

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