Pollution and external inputs

There is abundant evidence that intensification of crop, livestock and aquaculture systems through excessive use of synthetic inputs adversely affects BFA and particularly associated biodiversity (e.g. Angelini et al., 2013; Brodeur and Vera Candioti, 2017; Van Dijk et al., 2013; Geiger et al., 2010; Hussain et al., 2009; Pelosi et al., 2013;

White, 2017). The use of nutrient inputs in excess of efficient levels results in pollution of soil, air and water (e.g. Carpenter et al., 1998; van Dijk, Lesschen and Oenema, 2016). Although nutri-ent inputs in all forms may have negative effects when used in excess, nutrients carried in mineral fertilizers are particularly susceptible to ending up as pollutants, owing to their high concentra-tion and solubility (although not necessarily in the case of phosphorus fertilizers), their volatility (in some cases) and the changes they induce in the soil ecosystem when used for an extended period (changing the pH, promoting oxidation of organic matter, modifying soil biota, etc.) (e.g. Barak et al., 1997; Fonte et al., 2012; Guo, 2010; Mäder et al., 2008; Marschner, Kandeler and Marschner, 2003).

Contamination of soils with pesticide residues is also a major concern in intensive crop-production systems (FAO and ITPS, 2015; Rodríguez-Eugenio, McLaughlin and Pennock, 2018).

Intensive landless and intensive grassland-based livestock production creates large amounts of nutrient-rich effluent and solid residue, often containing high concentrations of antimicrobi-als, pathogens, heavy metals and other pollut-ants (FAO, 2006b; Maron, Smith and Nachman, 2013; Modernel, Astigarraga and Picasso, 2013).

Industrial and urban sources are also contributing to the contamination of soils with pollutants such as heavy metals and microplastics (Alloway, 2013;

Chae and An, 2018; Ng et al., 2018; Tóth et al., 2016;

Wuana and Okieimen, 2011). Other significant soil pollutants include persistent organic pollutants, polycyclic aromatic hydrocarbons, radionuclides and antimicrobial-resistant bacteria (Rodríguez-Eugenio, McLaughlin and Pennock, 2018). Human-induced salinity (see Section 3.6.1) and acidification are widespread problems, the former mostly

associated with inappropriate irrigation practices and the latter with high rates of ammonium-based fertilizer application (FAO and ITPS, 2015).

The diversity and functions of soil invertebrates and micro-organisms are known to be affected by the presence of excessive nutrients and by the use of herbicides and pesticides (Ceulemans et al., 2014; Ewald et al., 2015; Hussain et al., 2009;

Wolmarans and Swart, 2014). However, the pro-cesses involved are complex and a lot of uncer-tainty remains as to how particular substances, and combinations of substances, affect particular organisms and how these effects are influenced by environmental factors and by other manage-ment practices (Lo, 2010; Goulson, 2013; Sanchez-Moreno et al., 2015; Sebiomo, Ogundero and Bankole, 2011; Turbé et al., 2010; Wu et al., 2014).

Although research on the impact of microplastics in the soil is limited, there is evidence that they affect the biophysical environment and biodi-versity of the soil (Rochman, 2018; De Souza Machado et al., 2018). For example earthworms have been shown to have reduced growth rates and increased mortality if they ingest microbeads (Huerta Lwanga et al., 2016).

There is increasing evidence that some classes of pesticides threaten arthropod pollinators world-wide (IPBES, 2016a). High herbicide doses can be deleterious to the flora within and around agri-cultural fields (Egan and Mortensen, 2012; Gaba et al., 2016), with knock-on effects on biodiver-sity at higher trophic levels, for example insects and birds. One problem associated with pesticide use is the synergistic toxic effect that some mole-cules have when applied in mixtures. Most active ingredients are tested before they are released onto the market. However, the tests are done on the pure product in its commercial formulation (Brodeur et al., 2014). Most farmers, however, use such products in mixtures (e.g. a herbicide plus an insecticide in the same water suspension), and evi-dence obtained using biological indicators shows that some of the most common mixtures increase the toxicity of all active ingredients (ibid.). It is also important to note that the toxicity of active ingredients has increased over time, reducing the

dosage needed to have an impact (Letourneau, Fitzsimmons and Nieto, 2017).

A number of factors are driving increased use of pesticides and herbicides in some areas. For example, introduction of glyphosate-resistant genetically modified crop cultivars in North and South America and the Pacific led to greater use of glyphosate, leading in turn to the emergence of glyphosate-resistant weeds that resulted in the application of ever higher doses of this herbicide (Benbrook, 2012; Mortensen et al., 2012), with possible consequences for certain soil organisms (Van Bruggen et al., 2018; Gaupp-Berghausen et al., 2015). Pest pressures that trigger high doses of pesticide use appear to be increasing as a result of climate change (Cannon, 1998; Cilas et al., 2016;

Taylor et al., 2018).

The increasing contamination of freshwater systems with pathogens and chemical pollutants, including nutrients, is a major global threat to aquatic biodiversity (Dudgeon, 2012; Okano et al., 2018). The most significant problem affecting water quality globally is eutrophication caused by nitrogen and phosphorus runoff from agricultural land, flows of domestic sewage and industrial effluents, and atmospheric inputs from fossil-fuel combustion and forest fires (FAO and IWMI, 2018;

Russi et al., 2013; UN Environment, 2016a). Lakes throughout the world are affected by eutrophi-cation, and those in some regions (Scandinavia, northeastern United States of America/eastern Canada and China) are affected by acidification (Gleick, Singh and Shi., 2001). Lakes and reservoirs are particularly susceptible to the effects of pollu-tion, as the water that flows into them carrying sediments, dissolved nutrients and other pollutants normally remains standing for some time, leading to problems such as algal blooms, other species invasions and hypoxia (Speed et al., 2016). An issue that has recently been receiving increasing atten-tion is nitrate accumulaatten-tion in the vadose zone (i.e. the part of the Earth’s crust situated above the aquifers) in areas where highly intensive agricul-ture is practised. Ascott et al. (2017) describe this as a latent “nitrate bomb” that could cause major damage to aquatic biodiversity if released.

It has been estimated that more than 80 percent of wastewater globally is released into the envi-ronment without adequate treatment (WWAP, 2017). Aquatic pollution is exacerbated when ecosystems such as forests, grasslands and wet-lands that provide water purification services are destroyed or degraded and when rivers lose their ability to self-purify due to changes in the biota that perform this function (Ostroumov, 2005;

WWAP and UN-Water, 2018). Problems are also caused by the operation of dams, which results in the discharge of water with low oxygen levels into downstream areas (WWF, 2004). Another concern is the passage of personal-care products and pharmaceuticals into the aquatic environment via domestic sewage. Some of these pollutants contain microplastics (UN Environment, 2016b) and some are believed to mimic natural hormones in humans and other species (UN Environment, 2008; Vilela, Bassin and Peixoto, 2018).

Seawater quality and marine and coastal bio-diversity all around the world are also seriously affected by pollution (FAO, 2011a). The problem is becoming increasingly widespread near heavily populated regions of Latin America and Southeast Asia, threatening marine food sources and the economic activities of coastal communities (UN Environment, 2008, 2016c). So-called “dead zones”

caused by excess nitrogen undermine fish pro-duction and other ecosystem services (Halpern et al., 2009).²⁸ Coastal pollution is one of the many threats facing coral reefs (see also Section 4.5.4).

For example, the Great Barrier Reef off the coast of Australia is seriously affected by nutrient and pes-ticide runoff from sugar-cane farming and other types of agriculture (Queensland Government, 2017; Schaffelke et al., 2017).

An emerging threat to marine wildlife is increas-ing pollution by microplastics. Microplastics (plastic particles of less than 5 mm in diameter) are classified into two groups. Primary microplastics are plastics

28 such effects (and those noted above for freshwater and terrestrial systems) are among those that led rockström et al. (2009) to conclude that the earth may have crossed the so-called planetary boundary (i.e. the upper tolerable limit) for the disruption of its nitrogen and phosphorus cycles.

103

the state of the WorlD's bioDiversit y for fooD anD agriculture

directly released into the environment in the form of particulates smaller than 5 mm, while second-ary microplastics originate from the degradation of larger plastic items once exposed to the marine environment (Boucher and Friot, 2017). The global release of primary microplastics into the ocean is estimated at around 1.5 million tonnes per year (ibid.). Given the large amount of plastic entering the ocean, it is assumed that secondary microplas-tics are far more prevalent, but because fragmen-tation rates of plastics are largely unknown, there are no estimates available for the amount of

sec-ondary microplastic present (Duis and Coors, 2016;

Koelmans et al., 2014; Sundt, Schulze and Syversen, 2014). Ingestion of microplastics by aquatic fauna (fish, turtles, birds) has been shown to inhibit hatching, decrease growth rates and alter feeding patterns (Lönnstedt and Eklöv, 2016).

Information from the country reports on how pollution and external input use are driving changes in the supply of ecosystem services in specific production systems is summarized in Table 3.14.

Perhaps not surprisingly given the connota-tions of the word “pollution”, negative impacts table 3.14

Reported effects of pollution and external input use on the provision of regulating and supporting ecosystem services, by production system

Production systems (PS)

Effects of pollution and external inputs on ecosystem services

Pollination Pest and disease regulation Water purification and waste treatment Natural-hazard regulation Nutrient cycling Soil formation and protection Water cycling Habitat provisioning Production of oxygen/ gas regulation

livestock grassland-based systems - +/- - -

-livestock landless systems - - -

-Proportion of countries reporting

the Ps that report any effect of the

driver (%)

naturally regenerated forests - - -

-Planted forests - - -

-self-recruiting capture fisheries - - -

-Culture-based fisheries - - - 10–17

Fed aquaculture +/- - - +/- - - - ^18–25

non-fed aquaculture +/- - - +/- +/- - - ^26–33

irrigated crop systems (rice) - - - 34–43

irrigated crop systems (other) - - -

-rainfed crop systems - - -

-Mixed systems - - -

-Notes: Countries were invited to report the effects (positive, negative or “no effect”) of this driver on the provision of each ecosystem service in each production system. If 50% or more of the responses for a given combination of production system and ecosystem service indicate the same trend (positive [+], negative [-] or “no effect” [0]) then this trend is indicated in the respective cell of the table. In other cases, mixed effects (+/-) are indicated. The colour scale indicates the proportion of countries reporting the presence of the respective system that report any effect of the driver (positive, negative or “no effect”) on the provision of the respective ecosystem service. See Section 1.5 for descriptions of the production systems and a discussion of ecosystem services. Analysis based on a total of 91 country reports.

Source: Country reports prepared for The State of the World’s Biodiversity for Food and Agriculture.

are far more frequently reported than positive ones. Where positive impacts are reported and explanations provided, they normally relate to the benefits of using additional external inputs in systems where use is currently very low. Countries highlight a range of different effects. In the case of grassland systems for example, some European countries note that the overuse of nitrogen and phosphorus fertilizers is directly affecting species diversity. The report from the Netherlands, for instance, cites a study (Melman and Van der Heide, 2011) that found that the number of grass and herb species in unfertilized grasslands with relatively poor soils is between 20 and 30, while in fertilized grassland the number of species is between 5 and 15. The report further notes (citing LEI, 2015) that although average grassland fertilization rates in the Netherlands have declined, they still remain high.

Among examples from the crop sector, China men-tions the problem of so-called “white pollution”, i.e. pollution of the soil with plastic films used for mulching, and the negative effects of excess her-bicide use on the native flora surrounding agricul-tural fields. Egypt notes that the excessive use of fertilizers and pesticides has led to the decline of important components of agricultural biodiversity such as owls, kites and various pollinators.

Where aquatic ecosystems are concerned, many countries report that pollutants originating from crop and livestock production are negatively affecting biodiversity. For example, Spain reports that pollution from agricultural runoff has affected the composition and abundance of aquatic micro- organism communities and other components of aquatic biodiversity. It also notes that this pollution may alter the physical and chemical composition of the marine bed, influencing, in turn, the biologi-cal composition and structure of benthic commu-nities. Argentina mentions that agricultural runoff seems to be the most significant source of pollu-tion in aquatic ecosystems, noting in particular that soybean production is affecting wetland biodiver-sity in surrounding areas and is leading, inter alia, to changes in the population sizes of various aquatic organisms, changes in the physiology and behaviour of fish and amphibians, eutrophication of water

bodies and changes in the structure of riparian communities. The country reports provide little spe-cific information on pollution problems associated with aquaculture. However, Viet Nam reports that intensive aquaculture, in particular catfish farming in the Mekong Delta, has significantly contributed to eutrophication in surrounding waters.

Several countries note the impacts of pollut-ants from mining and other industries on aquatic ecosystems. For example, Zambia mentions that effluents from the mines of its Copperbelt and Northwestern provinces negatively affect the diversity of dragonflies and other benthic inver-tebrates in major river systems as a result of elevated levels of redox, electrical conductivity and turbidity.²⁹ Zimbabwe mentions that more than a million people are illegally panning for gold along its rivers and that this is resulting in the clearance of trees and digging in river beds, which in turn cause soil erosion and landslides that lead to the siltation of water bodies and destruction of aquatic biodiversity. It further notes that there has been an increase in the use of mercury, iron and cyanide to process ore and that this has polluted watercourses and affected the livelihood sources of local people. Mexico mentions that oil spills in the Gulf of Mexico have caused tremendous damage to marine and coastal ecosystems, biodiversity and economic activities such as fishing and aquaculture.

3.6.3 Overexploitation and