Growing pressures on ecosystems (GMT 8)

Drivers 

Population, consumption, and economic growth

The past five decades have seen a rise in the global population to more than 7 billion people, and a concomitant industrialisation of agriculture (GMT 1).^[1] About 2 % of the global land area is currently covered by cities and infrastructures.^[2] However, continued population growth and urbanisation (GMT 2) might cause this to double by 2050.^[2] In addition, continued global economic growth (GMT 5), accompanied by a rapidly growing global middle class – with resource-intensive, developed-world mobility and consumption patterns (GMT 2) – is likely to increase pressure on habitats and landscapes, particularly in regions with a high and direct dependence on natural resources for economic development, such as sub-Saharan Africa.^[3]

Food and bioenergy

Dietary changes might override population growth as the major driver of global demand for land in the near future.^[5] Meat-based food requires about five times as much land per unit of nutritional value as its plant-based equivalent,^[6] and also has a higher water footprint which is, on average, 20 times higher for beef than for cereals.^[7] Since the 1960s, global average meat consumption has almost doubled, from 23 kg per person to 42 kg, with the highest consumption in the US and Europe, while China and Brazil have recorded significant increases in the last 20–30 years.^[8] Estimates suggest that global annual demand for meat products may increase by a further 76 % relative to 2005 to 455 million tonnes in 2050.^[9]

A rapid expansion in land allocated to cultivating bioenergy crops (GMT 7) could have significant ecological impacts, such as deforestation, nitrogen pollution (GMT 10) and freshwater scarcity – the water footprint associated with bioenergy crops might increase ten-fold in the period 2005–2030.^[10] Mitigating associated pressures on ecosystems will depend on the development of bioenergy produced from agricultural and forestry residues that do not require additional land.^[11]

Increases in crop yields due to efficiency gains are unlikely to compensate for the growing demand for both plant- and animal-based food, and bioenergy. This could lead to a large-scale expansion of cropland, mostly at the expense of forest and grassland ecosystems, of 120–500 Mha (million hectares) by 2050 on top of the current 1 500 Mha of global cropland – 10 % of the global land area. Furthermore, if loss of productive land to severe soil degradation and conversion to built-up areas is taken into account, cropland expansion could reach 850 Mha by 2050.^[2]

Competition for land and water

Growing global competition for productive land and freshwater resources is apparent in the recent rapid increase in large-scale transnational land acquisitions, mostly in developing countries (Figure 1). Between 2005 and 2009, global land acquisitions by foreign investors totalled some 47 Mha,^[12] slightly more than the area of Sweden. As a consequence, large-scale commercial farming is expanding at the expense of smallholder farmers and their access to land and water - in particular in Africa and parts of Asia.

Population growth, demand for food and climate change are expected to create significant threats to freshwater availability.^[13] Scenarios on global food demand for 2050 point to severe water stress in many regions, even if strong efficiency gains in its use are made.^[14] This implies a threat to both human water security and to the functioning of ecosystems. Already today, around half of the world's major river basins, home to 2.7 billion people, face water scarcity in at least one month a year,^[15] and water restrictions are projected to be further amplified by climate change (GMT 9).

Figure 1: Transnational land acquisitions, 2005-2009^[12]

Data sources: Rulli et al., 2013 - [a] and [b]
Note: Please read reference [16] for additional information.

Trends

Terrestrial biodiversity

Some scenarios, including from the Organisation for Economic Co-operation and Development (OECD), consistently project a continued decrease of global biodiversity^[3] (Figure 2). Towards the mid-21st century, habitat loss due to bioenergy-crop farming and climate change is expected to gain in significance as drivers of decrease.^[3][17] In a business-as-usual scenario for 2050, global terrestrial biodiversity measured as mean species abundance (MSA) is projected to decline further: from 68 % of the level that potential natural vegetation could support in 2010 to around 60 % in 2050. Strong losses may occur in, for example, in Japan/Korea, Europe, southern Africa, and Indonesia (Figure 2). These estimates may be conservative, as they exclude risks associated with transgressing possible ecosystem thresholds (Box 1) and the increasing spread of some invasive alien species because of climate change.^[18]

Figure 2: Terrestrial mean species abundance, globally and for selected world regions, 2010–2050^[3] 

Data source: OECD Environmental Outlook to 2050
Note: Please read reference [19] for additional information.

Box 1: Thresholds and tipping points
There is evidence that ecosystems may need to maintain a minimum quality in order to function effectively. Below critical thresholds, ecosystems may suddenly switch in character, no longer providing the same kind, or level, of services.^[20] Thresholds, amplifying feedbacks and time-lag effects leading to tipping points make the impacts of global change on biodiversity hard to predict and difficult to control once they begin.

An area of particular concern in this regard is the Amazon basin, where recent research suggests that complex interactions between deforestation, fire and climate change could lead to a shift to savannah-like vegetation.^[21] Global-scale impacts of such a shift would include a reduced carbon sink, increased carbon emissions, and the massive loss of biodiversity.^[21] Some studies even suggest that a planetary-scale tipping point, implying radical changes in the global ecosystem as a whole, might be approaching.^[20]

Forests, drylands and wetlands

Demand for land has resulted in alarming tropical deforestation in recent decades. While overall global tropical deforestation remains high, some countries such as Brazil and Indonesia have slowed their rates. Mainly because of afforestation in temperate areas, some models project net global forest loss to halt after 2020.^[3] While plantations provide ecosystem services such as provisioning timber and carbon sequestration, they fall short of primary forests in delivering others, particularly forest biodiversity. Primary forests are projected to decrease steadily up to 2050, with the regions of most concern being Africa, Latin America and the Caribbean, and South East Asia.^[11][22]

Likewise, drylands and wetlands are threatened by depletion and loss of biodiversity. Drylands cover about 40 % of the Earth's surface and host about 2 billion people, but their transformation into cultivated cropland continues at alarming rates, resulting in water stress and soil degradation. Very high rates of irreversible conversion of peatland and coastal wetlands such as mangroves for agriculture, forestry and infrastructure are also likely to continue.^[11]

Marine ecosystems

In recent decades global marine ecosystems and their biodiversity have become increasingly threatened. In 2011, around 29 % of marine fish stocks were estimated as fished at a biologically unsustainable level and, therefore, overfished. In the same year, about 61 % were fully exploited and only 10 % held potential for increased harvesting.^[23] In addition to threats from overexploitation and nutrient pollution (GMT 10), ocean warming and acidification are projected to pose serious and increasing risks (GMT 9). Modelling of alternative marine fishery strategies up to 2050 indicates that marine catches and stocks will decline in the world's main fishing regions unless catches are reduced.^[24]

Implications

Loss of ecosystem services 

Global and regional assessments indicate that biodiversity loss and ecosystem degradation will continue or accelerate under all policy scenarios considered.^[21][25] The drivers of biodiversity loss are likely to greatly outweigh the effects of any biodiversity protection measures.^[25] Ecosystem degradation erodes nature's ability to support human societies,^[26] as ecosystems provide a wide range of services^[27][28] and indeed escalating competition for food, water and other natural resources could foster regional instability, increasing risks of conflict.

The benefits of protecting ecosystems and their associated services often far outweigh the costs.^[26][29] However, market systems seldom convey the full social and economic values of ecosystem services. 

Reduced climate change mitigation potential and adaptive capacity

The carbon captured by natural ecosystems is of global importance in efforts to mitigate climate change (GMT 9). As global forest destruction currently contributes about 12 % of global carbon dioxide emissions annually,^[30] the efficient protection of natural habitats could contribute substantially to continued carbon storage. In view of this, an international financial mechanism for reducing greenhouse gas emissions from deforestation and forest degradation, REDD+, has been adopted.^[31]

Ecosystem-based approaches that rely on ecosystems to buffer human communities against the adverse impacts of climate change would allow natural ecosystems to play an important role in climate change adaptation.^[32][33][34] Mangrove forests and coastal marshes, for example, can reduce disaster risks along exposed coastlines. And as the climate changes and temperatures increase (GMT 9) the need for ecosystem-based adaptation will increase.^[35]

Unequal distribution of impacts 

The continued degradation of ecosystems and their services will create challenges, in particular for lower income groups in developing countries. It is estimated, for example, that non-market ecosystem goods and services account for 89 % of the total income of the rural poor in Brazil, 75 % in Indonesia and 47 % in India. Sustainable management of ecosystems and socio-economic development are thus intertwined.^[26][36][37]

For Europe, the effects of continued ecosystem degradation on poverty and inequality elsewhere in the world may lead to increased immigration to Europe. In addition, failing to take advantage of ecosystem-based solutions to tackle climate change in other parts of the world may increase costs in Europe. And crucially, transgressing critical ecological tipping points could cause unprecedented environmental, social and economic problems in Europe and elsewhere.