copy the linklink copied!Chapter 2. Global biodiversity loss and the international context

Biodiversity has declined rapidly over the last 50 years, with severe implications for human health and well-being, societal resilience and sustainable development. This chapter summarises the international policy context for the conservation and sustainable use of biodiversity. Drawing on a range of data and indicators, it outlines the main pressures on biodiversity globally, and examines trends in the state of terrestrial, marine and freshwater biodiversity.


copy the linklink copied!2.1. Biodiversity picture and international context

Over the last 50 years, humanity has unleashed unprecedented technological change and economic growth, which have raised living standards and pulled billions of people out of poverty. However, the increasing demand for energy, food, fibre, water and land has come at a significant cost to planetary systems (Steffen et al., 2015[1]). The sheer scale of production and consumption, combined with systemic inefficiencies, misallocation of resources and waste, has resulted in rapid and widespread biodiversity loss. The implications for human health and well-being, societal resilience and sustainable development are considerable and potentially even catastrophic. According to the 2019 Global Risks Report, decision makers consider biodiversity loss and ecosystem collapse one of the ten greatest risks facing society today (WEF, 2019[2]).

Biodiversity underpins human life. It is responsible for a myriad of ecosystem services upon which society depends for basic life-support functions, such as the provision of food, fuel and clean water, nutrient cycling, pollination services and climate regulation (Box 2.1 and Figure 2.1). Halting biodiversity loss and restoring degraded ecosystems is therefore an essential element of sustainable development pathways. Failure to scale up action to address biodiversity loss will come at a significant cost to economies (Chapter 3) and businesses (Chapter 4), and more generally to human well-being.

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Box 2.1. Key terms and definitions

Biodiversity (biological diversity): “The variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems".

Ecosystem: “A dynamic complex of plant, animal, and microorganism communities and the non-living environment, interacting as a functional unit”.

Ecosystem services: “The benefits people obtain from ecosystems”.

Natural capital: “The stock of renewable and non-renewable natural resources (e.g. plants, animals, air, water, soils, minerals) that combine to yield a flow of benefits to people” .

Source: (United Nations, 1992[3]) (Millennium Ecosystem Assessment, 2005[4]) (Natural Capital Coalition, 2016[5])

Addressing biodiversity loss requires ambitious domestic action by governments and non-state actors, which can be amplified by strong international co-operation. The Group of Seven (G7) Environment Ministerial Meeting in 2019 takes place at a crucial time. In 2020, the Convention on Biological Diversity (CBD)’s Strategic Plan for Biodiversity 2011-2020 and its 20 Aichi Biodiversity Targets will expire. Governments will convene in China for the 15th meeting of the Conference of the Parties to the CBD (COP15) to agree on a post-2020 global biodiversity framework. The decisions made on the post-2020 framework will influence domestic goals and policies, and thus our collective ability to achieve not only Sustainable Development Goal (SDG) 14: Life Below Water and SDG 15: Life on Land, but also many of the other SDGs. For example, failure to address ongoing land-use change, deforestation and forest degradation will make the challenge of addressing climate change significantly more difficult. In turn, climate change will amplify the risks to biodiversity.

Although biodiversity loss is as great a challenge as climate change, it has received substantially less attention on the political agenda. The focus of the 2019 G7 meeting on biodiversity is a positive step forward. Biodiversity is connected intricately to other key themes that are more established on the G7 agenda, such as resource efficiency, climate change and marine litter. At the G7 Leaders Summit in 2018, for example, governments adopted the Charlevoix Blueprint for Healthy Oceans, Seas and Resilient Coastal Communities, which recognises the threat of plastic litter to marine ecosystems and the role of natural infrastructure (ecosystems) in building coastal resilience.1

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Figure 2.1. Types and examples of ecosystem services
Figure 2.1. Types and examples of ecosystem services

Source: Adapted from (OECD, 2010[6])

copy the linklink copied!2.2. Threats and pressures on biodiversity

Biodiversity faces a wide number of threats, including land-use change, habitat loss and fragmentation (e.g. due to agricultural expansion), over-exploitation of natural resources (e.g. unsustainable logging, hunting and fishing), pollution (e.g. excess fertiliser use and marine litter), invasive alien species and climate change (OECD, 2012[7]; SCBD, 2014[8]). For example, an analysis of over 8 500 threatened or near-threatened terrestrial, freshwater or marine species found that 72% are overexploited, and 62% are affected by agriculture (crop and livestock farming), timber plantations and/or aquaculture (Maxwell, 2016[9]). Agricultural expansion and intensification continues to be the dominant pressure on terrestrial biodiversity, and is expected to increase as the demand for food and bioenergy grows (SCBD, 2014[8]). These impacts are exacerbated by international trade, which tends to shift the environmental impacts of production from developed to developing countries (Krausmann and Langthaler, 2019[10]). For example, 33% of biodiversity impacts in Central and South America and 26% in Africa are driven by consumption in other regions (Marques et al., 2019[11]).

Unsustainable fishing remains a major threat to marine ecosystems. Over 30% of fish stocks are fished at biologically unsustainable levels (Figure 2.2) (FAO, 2018[12]), and sea-bed bottom trawling is destroying irreplaceable deep-water habitats. Pollution from fertiliser run-off and sewage disposal also poses a threat to marine biodiversity, as reactive nitrogen and phosphorous can cause algal blooms, anoxic conditions and acidification. There is also growing concern about plastics pollution, with an estimated 8 million tonnes of plastic entering the ocean each year (Jambeck et al., 2015[13]), and documented impacts on around 500 species of marine mammals, fish and seabirds (SCBD, 2016[14]). Meanwhile, ocean warming and acidification are intensifying with climate change (IPCC, 2018[15]).

Climate change is putting increasing pressure on marine and terrestrial biodiversity, and exacerbating not only ocean warming and acidification, but also other pressures such as invasive alien species (Early et al., 2016[16]). A synthesis of hundreds of scientific studies found that climate change has already resulted in shifts in species distribution and disrupted species interactions, led to mismatches in the timing of migration, breeding and food supply, and contributed to declines in populations (BirdLife International and The National Audubon Society, 2015[17]). Climate change is also affecting ecosystem configuration, productivity and service provision, with significant economic implications (Lipton et al., 2018[18]). In the absence of ambitious climate action, the impacts on biodiversity and ecosystem services will be severe: coral reefs are projected to decline by a further 70-90% with global warming of 1.5Celsius above pre-industrial levels, or by more than 99% if the world allows warming of 2Celsius (IPCC, 2018[15]).

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Figure 2.2. Global trends in the state of world marine fish stocks, 1974-2015
Figure 2.2. Global trends in the state of world marine fish stocks, 1974-2015

Source: (FAO, 2018[12]).

copy the linklink copied!2.3. State of terrestrial, marine and other aquatic biodiversity

The multidimensionality and complexity of biodiversity means there is no single measure that can comprehensively capture the state of biodiversity globally. However, a range of biodiversity data and indicators on species, forests, wetlands and other ecosystems clearly point to an overall decline in biodiversity and the widespread degradation of ecosystems. While overall trends are negative, there exist a few notable examples of effective conservation and sustainable use of biodiversity, demonstrating that progress has been made, and that humankind has the knowledge and tools to address biodiversity loss.

2.3.1. Trends in species and populations

The planet is facing its sixth mass extinction. Scientists estimate the current rate of species extinction to be as much as 1 000 times higher than the natural background (pre-human) rate (De Vos et al., 2015[19]).2 In the 20th century alone, 477 vertebrates are known to have gone extinct, while only nine would have been expected to go extinct if background rates of vertebrate extinction had persisted (Ceballos et al., 2015[20]). Species extinction not only represents an irreversible loss of global diversity and its inherent value, it has negative knock-on effects for ecosystem function, productivity and resilience (Cardinale et al., 2018[21]).

Of the 96 500 species on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species,3 26 500 (more than 27%) are threatened with extinction. This includes 40% of amphibians, 34% of conifers, 33% of reef corals, 31% of sharks and rays, 27% of selected crustaceans and 14% of birds. The total number of species threatened with extinction is likely to be much higher, as the Red List only covers a portion of the world’s species: many (particularly non-vertebrate) species are yet to be formally identified, and gaps in available data and information remain.

In addition to species extinction, the widespread and frequent loss of populations, and declines in the numbers of individual species within remaining populations, are also cause for concern. Species abundance, not just diversity, is an important determinant of ecosystem function and resilience (Valiente‐Banuet et al., 2015[22]) (Oliver et al., 2015[23]), and the delivery of ecosystem services (Inger et al., 2014[24]) (Winfree et al., 2015[25]). The Living Planet Index (Figure 2.3), which tracks the population abundance of thousands of mammals, birds, fish, reptiles and amphibians around the world, shows an overall decline in population sizes of 60% between 1970 and 2014 (WWF, 2018[26]). Globally, freshwater species show the largest declines, with an 83% loss in population size since 1970.

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Figure 2.3. Living Planet Index, 1970-2014
Figure 2.3. Living Planet Index, 1970-2014

Source: (WWF, 2018[26]).

Population declines are affecting not only rare and threatened species, but also common ones. In Europe, for example, common farmland birds declined by 57% between 1980 and 2016 (EBCC et al., 2017[27]). Similar trends exist in Canada and the United States, where 74% of farmland bird species declined between 1966 and 2013 (Stanton, Morrissey and Clark, 2018[28]). The causes of these declines include loss of natural habitats, mowing/harvesting, exposure to pesticides and a decline in the insects upon which most birds depend. For example, flying-insect biomass in 63 protected areas in Germany declined by more than 75% over 27 years (Hallmann et al., 2017[29]). Globally, 40% of insects are in decline and one-third are threatened with extinction (Sánchez-Bayo and Wyckhuys, 2019[30]). In addition to its impacts on the food web, the loss of insect biomass and diversity negatively affects crop pollination, waste disposal and nutrient cycling (Losey and Vaughan, 2006[31]).

2.3.2. Trends in the extent and state of ecosystems

Humans have transformed the majority of terrestrial, marine and other aquatic ecosystems across the globe. Ecosystems and the habitats they provide continue to be converted, degraded and fragmented, altering their function, productivity and resilience.

Global forest cover continues to decline as demand for food and land increases (Hansen et al., 2013[32]). Planted forests have increased, but this increase has been offset by a decline in natural forests (FAO, 2019[33]), which tend to be more biodiverse (Gibson et al., 2011[34]). Natural forest area declined by 10.6 million hectares per year from 1990 to 2000, and by 6.5 million hectares per year from 2010 to 2015 (FAO, 2019[33]). Natural wetland coverage has declined by an estimated 35% over 1970-2015 (Figure 2.4) (Darrah et al., 2019[35]), and continues to decline at a rate of 0.85-1.6% per year (Ramsar Convention on Wetlands, 2018[36]). The fragmentation of forests, wetlands and other habitats is also concerning, as it is a precursor of species loss and disrupts ecosystem functions by decreasing biomass and altering nutrient cycles (Haddad et al., 2015[37]). Habitat fragmentation is expected to become increasingly problematic with climate change, as it undermines the ability of species to track suitable habitats (SCBD, 2009[38]).

The state of marine and coastal ecosystems has also deteriorated. For example, global mangrove area is estimated to have declined by about 20% between 1980 and 2005 (FAO, 2007[39]), and the coverage of seagrass is estimated to have declined by 29% over the last 100 years (Waycott et al., 2009[40]). The world lost approximately half of its shallow water corals in the past 30 years (WWF, 2018[26]), and 31% of the world’s corals are now at risk from bleaching, compared to 8% in the 1980s (Hughes et al., 2018[41]). While severe bleaching events used to occur every 27 years, the median time between events had declined to 6 years by 2016 (Hughes et al., 2018[41]).

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Figure 2.4. Global and regional trends in natural wetland coverage, 1970-2015
Figure 2.4. Global and regional trends in natural wetland coverage, 1970-2015Figure 2.4. Global and regional trends in natural wetland coverage, 1970-2015

Note: Wetlands Extent Trend index for global marine/coastal and inland wetlands, and for natural wetlands in six regions. Natural regional wetland trends are reported from 1970 to 2015 except for Europe (1970-2013) due to data availability. The dashed lines for the global index show 95% confidence intervals.

Source: Based on data from (Darrah et al., 2019[35]).

The widespread destruction, degradation and fragmentation of ecosystems is accelerating, with profound implications for human well-being and the global economy. The loss of biodiversity already costs the world billions of dollars per year (Chapter 3). Moreover, because ecosystems are complex, non-linear systems, incremental increases in pressure in the coming years could have a disproportionately large impact on biodiversity and the ecosystem services upon which economies and human well-being depend.

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Box 2.2. Ecosystem thresholds and tipping points

Ecosystems can only absorb pressure up to a certain threshold. Beyond this threshold, an incremental increase in human pressure can lead to a large, often abrupt, change in an ecosystem’s structure and function. Such abrupt regime shifts tend to be persistent and irreversible (or costly to reverse), and can have profoundly negative environmental, economic and social consequences.

Thresholds are expected to be crossed more frequently in the coming decades in marine, freshwater and terrestrial ecosystems owing to the increasing intensity of pressures, and their combined and often synergistic effects. The complex non-linear dynamics of ecosystems and their interactions with human systems make it difficult to predict where thresholds lie, when they will be crossed, and what will be the scale of impact. Given this uncertainty and the potential impact of regime shifts, it is prudent to take a precautionary approach and keep disturbance well below likely thresholds. Maintaining or restoring biodiversity can make ecosystems more resilient, reducing the likelihood of regime shifts.

Source: (Folke et al., 2004[42]) (Leadley et al., 2014[43]) (Scheffer et al., 2001[44]).


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← 1. For a discussion of coastal resilience and marine plastics in the context of G7, see (OECD, 2018[45]) and (OECD, 2018[46]).

← 2. There are uncertainties and variations in estimates of current and background extinction rates, which stem from the difficulty of estimating background extinction rates e.g. through fossil records and molecular phylogeny. However, estimates consistently indicate a notable increase in the extinction rate.

← 3. The Red List of Threatened Species (established in 1964) is a widely used indicator of the health of the world’s biodiversity. It uses a set of quantitative criteria to evaluate the extinction risk of thousands of species. It divides species into nine categories: Not Evaluated, Data Deficient, Least Concern, Near Threatened, Vulnerable, Endangered, Critically Endangered, Extinct in the Wild and Extinct.

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