5.4.1 Food systems and deforestation
Deforestation is continuing, with tropical, rather than temperate, forests most affected since the early 20th century
Deforestation for human purposes has a long history. Historically, deforestation has often gone hand-in-hand with human population growth and development. Up until the 20th century, most of this growth, development and therefore deforestation took place in temperate regions.
More recent deforestation has taken place in tropical regions, particularly in South America and South East Asia but also in Africa.
What effect do food systems have on deforestation and forest degradation?
Kissinger, Herold and De Sy (2012)
Agriculture has historically been the biggest driver of deforestation, responsible for about 80% of deforestation in the key tropical regions of the world (Africa, Latin America and subtropical Asia). The main driver of deforestation in Latin America has been commercial agriculture, but in Africa and subtropical Asia, subsistence farming has played a significant role. In contrast, forest degradation (where forests deteriorate through mismanagement, rather than the forest being cleared for alternative use) is caused more by timber logging and fuelwood than by agriculture.
Growing demand for food is expected to further increase pressure on forest.
Why does deforestation matter?
Land-use change from forest to agriculture releases carbon stocks held in forests.
The release of carbon contributes to global GHG emissions.
Land-use change also causes significant biodiversity loss.
CO₂ is released when carbon stocks such as forests are cleared for agricultural purposes – see Chapter 3 for a discussion of how significant this is in relation to overall food GHG emissions.
The benefits of halting deforestation are significant, potentially reducing global GHG emissions by around 3 gigatonnes per year in 2030. To put this in context, total global GHG emissions in 2010 were 49 gigatonnes carbon dioxide equivalent (GtCO2eq).
Restoring degraded agricultural land by 12% could also reduce GHG emissions by up to 2 gigatonnes per year.
Deforestation contributes to significant biodiversity loss (see below).
5.4.2 Food systems and biodiversity loss
Biodiversity loss from wider agricultural impacts
Adapted from NEAA (2010)
Without action, increased demand for food, and in particular for resource-intensive food such as meat, will lead to significant and continued biodiversity losses. This would primarily arise from agricultural expansion into new areas to grow crops (often to feed livestock), from the creation of new pasture lands, and encroachment on and fragmentation of ecosystems. Note that a degree of uncertainty exists around population growth, demand for food, and how food production responds to these changes. For discussions about expected population change, see Chapter 1, Chapter 4 and Chapter 7.
These biodiversity losses could be modified or reduced by increasing the extent of protected areas, through yield increases in food production, better forest management, by actions to moderate demand for resource-intensive food consumption, and by limiting climate change. Some of these options are explored in Chapter 4, in relation to addressing greenhouse gas emissions.
5.4.3 Food systems and soil degradation
Deforestation, climate change and unsustainable soil management practices all contribute to soil degradation
Poor management of agricultural soils combined with other environmental drivers can lead to degradation of soils, including (but not limited to):
Salinisation: the accumulation of soluble salts of sodium, magnesium and calcium in soil to the extent that soil fertility is severely reduced (see).
Compaction: the result of physical pressure exerted on soils, e.g. by heavy farm machinery which leads to air spaces between soil particles being reduced, resulting in poorer water infiltration and drainage.
Acidification: the gradual reduction in soil pH as the result of acids in rain or produced by fertilisers.
Organic carbon loss: Soil organic carbon, from living or dead and decaying organisms in the soil, plays several crucial roles in soil function. According to this fact sheet by the Joint Research Centre of the European Commission, “Soil organic matter is a source of food for soil fauna, and contributes to soil biodiversity by acting as a reservoir of soil nutrients such as nitrogen, phosphorus and sulphur; it is the main contributor to soil fertility. Soil organic carbon supports the soil’s structure, improving the physical environment for roots to penetrate through the soil.” Organic matter also absorbs and holds water, improving drainage and soil structure. Threats to soil organic matter (i.e. processes that lead to its reduction) include: soil temperature rises (linked to both climate change and tillage), waterlogging and the physical removal of vegetation (including crops every harvest) without replacement of the organic matter.
5.4.4 Direct impacts of agriculture on wildlife and ecology
In addition to the indirect impacts of agriculture on wildlife – through its contributions to deforestation, climate change and other forms of environmental damage – agriculture can also have direct localised impacts on the wildlife sharing the farmland. For example, Benton et al. (2003) present the above scheme showing the various ways in which bird populations on a local up to a national scale may be affected by agricultural activities.
Direct impacts of agriculture on wildlife
Another currently relevant example is that of the link between neonicotinoid pesticides and declining global bee populations. A number of studies have provided evidence that bees of various species are directly adversely affected by such pesticides – for example, Whitehorn et al. (2012) exposed bumble bee (Bombus terrestris) colonies to field-realistic concentrations of a neonicotinoid pesticide then allowed the colonies to develop in field conditions. They found that the colonies had a significantly impaired growth rate, as well as producing 85% fewer queen bees than untreated colonies. Godfray et al. (2015) summarised and reviewed the latest advances in the scientific understanding of the relationship between neonicotinoids and pollinating insects and reported that:
- There is evidence that residues of the neonicotinoid pesticides applied to crop seeds, which become distributed throughout the plant as it grows, can be detected in pollen and nectar produced by the plants, although there is a wide variation in the reported concentrations in the literature.
- There is some literature (limited in number of data and in species considered) reporting that neonicotinoid pesticide residues can be detected in wild pollinators as well as in honeybee and bumblebee colonies.
- While some studies find that pollinators can be exposed to lethal levels of neonicotinoid pesticides, most exposures are found to be at sub-lethal levels. However, multiple studies report behaviourally and physiologically detrimental effects of these sub-lethal dosages, although the range of dosages and the range of reported effects are both very wide.
As a result of the evidence available, the EU has placed restrictions on the use of nicotinoid pesticides, although exceptions can be granted in geographically specific areas where viable alternatives are not available.
5.4.5 Multi-scale impacts of agricultural intensification
Multi-scale impacts of agricultural intensification
- As has been shown above, agricultural intensification and expansion can contribute to land use change and biodiversity loss in its immediate vicinity.
- However, the impacts of all agricultural activities must be viewed across multiple scales.
- Intensification may be associated with negative impacts at the field scale but additionally impacts (potentially positive or negative) on the farm, landscape, country, regional or even global scale may also arise.
- For example, agricultural intensification by one farm may free up land for wildlife conservation elsewhere in the same or even another country (so called ‘land-sparing’). This may benefit wildlife. On the other hand, productivity increases arising from intensification may, by increasing food supply, drive down prices, so stimulating demand and triggering further production, thereby undermining the land sparing gains.
- Similarly, adoption of more ‘wildlife-friendly’ farming may be associated with lower yields, thus requiring the additional cultivation of land elsewhere within the same country, or importing of food from other countries (potentially associated with land use change and biodiversity loss in the exporting country). On the other hand, wildlife friendly farming could in principle be implemented in parallel with more systemic shifts towards the consumption of less resource and land intensive foods, thereby reducing the ‘leakage’ effect.
- It may be argued that individual farms undergoing intensification and causing localised biodiversity loss may contribute on a wider landscape scale to disproportionately damaging habitat fragmentation; that is, the breaking up of continuous habitat into smaller more isolated patches.
FOEN and EEA (2011)
In addition to simply reducing habitat area, habitat fragmentation poses multiple additional threats to biodiversity: for example, so-called ‘edge effects’ caused by the simple geometric fact that a fragmented habitat will have more exposed edges than a continuous habitat of the same total area. This can drastically alter the species composition of the area since the interior habitat area is reduced (amounting to habitat loss for the species that depend on it) while edge habitat area increases (amounting to habitat expansion for edge species, which may be more versatile/adaptable anyway) (see diagram).