Pollution can take many forms (e.g. waste and chemical products deliberately or accidentally released into the environment, but also light, noise, heat and microbes); major emitters include transport, industry, agriculture (Landrigan et al. 2017) and aquaculture (Klinger and Naylor 2012; Bouwman et al. 2013). Emerging pollutants include a wide range of synthetic chemicals, pesticides, cosmetics, personal and household care products, and pharmaceuticals (Gavrilescu et al. 2015; Landrigan et al. 2017).
Marine litter, including marine plastic litter and microplastics, is considered a major threat to biodiversity, with serious impacts reported over the last four decades (SCBD 2012). Recent research shows that more than 800 marine and coastal species are now affected through ingestion, entanglement, ghost fishing or dispersal by rafting (SCBD 2016). Between 2012 and 2016, aquatic mammal and seabird species known to be affected by marine litter ingestion increased from 26 per cent and 38 per cent to 40 per cent and 44 per cent, respectively (SCBD 2016). Plastics, which constitute 75 per cent of marine litter, have been shown to act as carriers for persistent bioaccumulative and toxic substances (PBTs); provide habitats for unique microbial communities; act as a potential vector for disease; and provide a means to transport invasive alien species across oceans and lakes (Rochman et al. 2013; SCBD 2016). Research on the physical and toxicological effects of microplastic provides evidence of trophic transfer in planktonic food chains as well as the direct uptake of microplastics by marine invertebrates (Wright, Thompson and Galloway 2013; SCBD 2016). Ingestion of microplastic by fish has been shown to cause physiological stress, liver cancer and endocrine dysfunction, affecting female fertility and the growth of reproductive tissue in male fish (Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection [GESAMP] 2015). According to the United Nations, 51 trillion microplastic particles, 500 times more than stars in our galaxy, litter our seas, seriously threatening marine wildlife (van Sebille et al. 2015).
On land, open waste dumps have local impacts on plants and animals (see Chapter 8), and soil pollution can affect the microbial population and reduce important ecosystem functioning (Wall, Nielson and Six 2015). Pesticides, fertilizers and other chemicals used in agricultural processes can harm pollinators and natural predators of pests (Woodcock et al. 2016), with surface run-off also impacting freshwater and coastal biodiversity (see Chapters 7 and 9). Bioaccumulation of toxins, including heavy metals (Araújo and Cedeño-Macias 2016), may have cascading impacts across the entire food chain, including humans. In marine and freshwater environments, the accumulation of microplastic and nanoplastic pollution (see Chapter 7 and Box 6.2) has been identified as an emerging issue (SCBD 2016).
The accumulation of endocrine-disrupting chemicals (EDCs) and persistent organic pollutants (POPs) in natural ecosystems pose additional threats to wildlife (Bergman et al. eds. 2013), particularly in aquatic systems (Wang and Zhou 2013) (see Chapter 9).
Air pollution contributes to the acidification and eutrophication of terrestrial ecosystems, lakes, estuaries and coastal waters (O’Dea et al. 2017; Payne et al. 2017), and to mercury bioaccumulation in aquatic food webs (Lavoie et al. 2013) (see Chapter 5).