biodiversity for food and agriculture
4.3 Associated biodiversity
4.3.4 Associated biodiversity for pollination
Introduction
Nearly 90 percent28 of all flowering-plant species, including the vast majority of those in tropical forests, savannah woodlands, mangroves and temperate deciduous forests, depend, to some degree, on animal pollination (other means of pollen transfer include self-pollination and pol-lination by wind and water) (Bradbear, 2009;
Ollerton, Winfree and Tarrant, 2011).29 Thirty-five percent of the world’s total crop production by volume comes from species that are, at least in part, pollinated by animals (Klein et al., 2007).
Levels of pollinator dependence vary significantly among crops, with the highest levels found mainly in fruits, vegetables and nuts (ibid.). Potts et al.
(2016) report a figure of USD 235–577 billion for the annual value of the enhancements that animal pollinators make to global crop output.30
28 This ranges from 78 percent in temperate-zone communities to 94 percent in tropical communities (IPBES, 2016a; Ollerton, Winfree and Tarrant, 2011).
29 Pollination also occurs in aquatic environments. While until recently it was thought that animal pollination does not contribute to pollination under water, it has been found that marine invertebrates contribute to the pollination of the seagrass Thalassia testudinum (Van Tussenbroek et al., 2016).
30 The figure (inflated to 2015 USD value) is based on the work of Lautenback et al. (2012), who used production and price figures for 2009.
Animal pollination in crop production systems is largely supplied by managed and wild bee species.
However, there are important pollinators among other groups of insects, including flies, butterflies, moths, wasps and beetles, as well as among bats, birds and rodents (FAO, 2018i, IPBES, 2016a).31 For example, it has been estimated that bats play some part in the pollination of at least 500 Neotropical species from 96 genera (Vogel, 1969). The role of
31 More than 90 percent of the leading global crop types are visited by bees and around 30 percent by flies. Each of the other animal pollinator taxa visits less than 6 percent of the crop types.
birds as pollinators is discussed further in Box 4.5.
Some species of pollinators are specialists (i.e. visit only one or a few plant species), while others are generalists (i.e. visit a wide range of species).
Similarly, there are specialist plants, pollinated by a small number of species, and generalist plants, pol-linated by a broad range of species (IPBES, 2016a).
State of knowledge
Scientific studies, citizen-science projects and indigenous and local knowledge all help to build up understanding of the economic, environmental and sociocultural values of pollination, threats to TABLE 4.4
Reported trends in the state of provision of regulating and supporting ecosystem services in production systems
Production systems (PS) 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 trends (%)
Naturally regenerated forests ↗↙ ↗↙ ↗↙ ↗↙ ↗↙ ↗↙ ↗↙ ↗ ↗↙
Planted forests ↗↙ ↗↙ ↗↙ ↗↙ ↗↙ ↗ ↗ ↗ ↗
Self-recruiting capture fisheries ↗↙ ↗↙ ↗↙ ↗↙ ↗↙ ↗↙ ↗↙
Culture-based fisheries ↗↙ ↗↙ ↗↙ ↘ ↗↙ ↗↙ ↗↙ 0–10
Fed aquaculture ↔ ↗↙ ↗↙ ↗ ↗ ↗↙ ↗ ↗↙ ↗↙ 11–20
Non-fed aquaculture ↗↙ ↗↙ ↗↙ ↗↙ ↔ ↗↙ ↗ 21–30
Irrigated crop systems (rice) ↗↙ ↘ ↘ ↔ ↘ ↘ ↘ ↘ ↗↙ 31–40
Irrigated crop systems (other) ↗↙ ↘ ↘ ↗↙ ↘ ↘ ↗ ↘ ↗
↔ Stable
↗ Increasing
↘ Decreasing
↗↙Mixed trends
Rainfed crop systems ↗↙ ↘ ↗↙ ↗↙ ↗↙ ↘ ↗↙ ↘ ↗↙
Mixed systems ↗↙ ↗ ↗↙ ↗↙ ↗ ↗↙ ↗↙ ↗↙ ↗↙
Notes: Countries were invited to report trends (increasing, stable or decreasing) in the state of 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 (increasing, decreasing or stable) then this trend is indicated in the respective cell of the table. In other cases, mixed trends are indicated. The empty cells correspond to cases in which fewer than five countries provided a response. The colour scale indicates the proportion of countries reporting the presence of the respective system that report any trends in the state of the respective ecosystem service (increasing, stable or decreasing). See Section 1.5 for descriptions of the production systems and a discussion of ecosystem services. Analysis based on 91 country reports.
Source: Country reports prepared for The State of the World’s Biodiversity for Food and Agriculture.
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pollinator populations, and the status and trends of wild and managed pollinators, pollinator- dependent crops and wild plants at various scales. At global level, the thematic assessment of pollinators, pollination and food production published in 2016 by the International Panel on Biodiversity and Ecosystem Services (IPBES, 2016a) remains, as of 2018, the latest major assessment conducted on the topic.
The availability of data on the status and trends of pollinators varies significantly by region, country and type of pollinator. Data are more complete in Europe and North America than elsewhere in the world. Within these regions, managed pollinator species are better docu-mented than wild pollinators, because they are (i) recognized as economically important, (ii) easier to monitor (they are kept in boxes) and (iii) their taxonomy is relatively well understood (IPBES, 2016a; NRC, 2007). A report on the status of pol-linators in North America (NRC, 2007) notes that despite constraints associated with a lack of capac-ity in taxonomy and identification, quite a large amount of information is available on pollinator population trends. However, the quality of this information, and hence the state of knowledge on status and trends, varies from taxon to taxon (ibid.). The IUCN Red List of Threatened Species assessment covers 58 out of the 130 common crop-pollinating bee species in Europe and North America (IPBES, 2016a).
The country reports indicate that, across all regions, bees are the most widely monitored group of pollinator species. Honey bees are the most fre-quently mentioned, but some countries also refer to monitoring of bumblebees, stingless bees and other (wild) bee species. Relevant initiatives men-tioned in the country reports include the bee monitoring framework developed in the United Kingdom as part of England’s National Pollinator Strategy (DEFRA, 2014). Numbers of beehives are widely monitored.32 Ethiopia, for example, notes that despite a general lack of information on
32 See, for example, the country data provided in FAO’s statistical database FAOSTAT (http://www.fao.org/faostat/en/#home).
managed associated biodiversity, its annual inven-tory of beehives provides a form of “indirect” mon-itoring. A number of countries mention that – as an alternative to gathering data on pollinating animals themselves – monitoring plant reproduc-tive success or pollen-deposition deficits may be an effective means of measuring pollinator trends.
However, this approach will only work if the effects of other influences, such as climate and floral her-bivory, can be accounted for (FAO, 2008a).
Butterfly monitoring, where it occurs, is reported to be largely conducted on a voluntary basis by experts and enthusiasts. For example, Germany notes that volunteers conduct weekly walks along set routes (transects), recording all species of diurnal butterflies, year after year.33 The population data obtained are used to track trends in butterfly populations at local, subnational and national levels. Butterflies are also among the groups of species reported to be monitored by the Dutch Network Ecological Monitoring34 pro-gramme in the Netherlands.35 Again, these data are mostly collected by volunteers. The results are published by, among others, the Netherlands Environmental Assessment Agency and Statistics Netherlands. Around 16 000 volunteers are reported to be active in the programme’s various monitoring networks.36 Ireland also mentions the establishment of butterfly and bumblebee moni-toring programmes.37
Information on the status and trends of other pollinators is generally limited. The IUCN Red List provides information on the global status of many vertebrate pollinators (e.g. humming birds and bat species). The migratory habits of species belonging to these groups sometimes require that monitoring work is done on a multicountry scale (FAO, 2008a).
Mexico and the United States of America are col-laborating in several initiatives of this kind (ibid.).
33 See, for example, http://www.tagfaltermonitoring.de (in German).
34 http://www.netwerkecologischemonitoring.nl/home
35 There are also networks for mammals, birds, reptiles, amphibians, fish, dragonflies, flora and mushrooms.
36 The country report cites De Groot (2014).
37 http://www.biodiversityireland.ie
Data on fly populations (Diptera) are limited (FAO, 2008a). However, some evidence can be gleaned from case studies (see below). Overall, the risk status of most of the world’s insect pollinator species has not been assessed (IPBES, 2016a).
Status and trends
Status and trends of pollinators
Data from FAO’s statistical database, FAOSTAT, show that the number of managed western hon-ey-bee hives is increasing globally. In 1961, coun-tries reported fewer than 50 million hives. In 2016, they reported more than 90.5 million hives, pro-ducing nearly 1.8 million tonnes of honey annu-ally. IPBES (2016a), however, notes that, despite the overall upward trends globally, important sea-sonal colony losses are known to occur in some European countries and in North America (data for other regions of the world are largely lacking).
Concerns about colony losses are reflected in some of the country reports. For example, the report from the United States of America notes that honey bees have been in serious decline for decades: there were approximately 5.7 million managed honey-bee colonies in the country in the 1940s and approximately 2.74 million colonies in 2015. It further notes that sharp colony declines occurred following the introduction of the mite Varroa destructor38 in 1987, and again around 2006 with the first reports of colony collapse disorder.39 The number of managed honey-bee colonies in the country seems to have stabilized in recent years, but this is reported to have required increased efforts by the beekeeping industry.40 Since 2006,
38 An external parasite that attacks honey bees and spreads viruses among them.
39 The term colony collapse disorder describes a complex set of interacting stressors, including exposure to pesticides and other environmental toxins, poor nutrition (resulting in part from decreased availability of high-quality and diverse forage), exposure to pests (e.g. Varroa mites) and disease (viral, bacterial and fungal) that cause high colony losses (USDA, 2012).
40 When overwintering colony losses are high, beekeepers compensate for these losses by “splitting” one colony into two and supplying the second colony with a new queen bee and supplementary food in order to quickly build up colony strength.
the average seasonal loss of honey bees in the United States of America has reportedly averaged around 31 percent, far exceeding the 15 percent to 17 percent loss rate that commercial beekeepers consider to be an economically sustainable aver-age.41 A few country reports from northwestern Europe mention that the state of insect colonies in general, and of bee colonies in particular, is cur-rently below the optimal threshold for pollination of flowering plants in arable land and grassland.
With regard to wild pollinators, IPBES (2016a) concludes that they “have declined in occurrence and diversity (and abundance for certain species) at local and regional scales in North West Europe and North America” and notes that while a lack of data precludes general statements about other regions, local declines have been recorded. In Europe, 9 percent of bee and butterfly species are threatened, and populations are declining in 37 percent of bee and 31 percent of butterfly species (excluding data deficient species, which include 57 percent of bee species [ibid.] ).42 Trends of this kind are reflected in the country reports from Europe. The report from the United Kingdom, for example, refers to work showing that among 216 bee species monitored nationally, 70 percent showed a decline in distribution between 1980 and 2010. With regard to the country’s butterfly populations, the report indicates that recent years (2008 to 2013) have seen no overall change, but that long-term figures (1976 to 2013) show that the populations of 50 percent of butterfly species have decreased. Several country reports from the region, including those from Ireland, Norway, Poland and Switzerland, refer specifically to a decline in bumblebees. Serious declines in two bumblebee species, the great yellow bumblebee (Bombus distinguendus) in Europe and Franklin’s bumblebee (B. franklini) in the western United States of America, are highlighted by IPBES (2016a).
In both cases, effects on production systems have yet to be examined (ibid.).
41 The country report cites Steinhauer et al. (2015).
42 Data for other regions are currently insufficient to draw general conclusions.
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Among countries from other regions, Brazil reports that its 1 173 species of fauna classified as being threatened with extinction include 85 bird species, 63 lepidopteran species, 29 beetle species, 7 bat species and 4 bee species that can be con-sidered pollinators. Some other countries report anecdotal indications of trends. For example, Grenada mentions that farmers frequently comment on falling numbers of butterflies and other insects in their fields, but notes that no spe-cific studies have been conducted to confirm this perceived change or to identify possible causes.
As noted above, data on population trends in insect pollinators other than bees and Lepidoptera are generally limited. However, some studies provide insights into local trends or drivers of change among relevant taxonomic groups. For example, Lagucki, Burdine and McCluney (2017) report negative effects of urbanization on flies (Diptera), among other groups of flying arthro-pods. Hallmann et al. (2017) report severe declines in total flying-insect biomass over recent decades at sites in Germany (see Box 4.3).
Where vertebrate pollinators are concerned, IPBES (2016a) estimates, based on data from
The IUCN Red List, that 16.5 percent of species are threatened with global extinction (increas-ing to 30 percent for island species), with a trend towards more extinctions. Regan et al.
(2015) report that among 1 089 bird species and 343 mammalian species identified as pollinators, 18 of the former and 15 of the latter moved into a higher IUCN Red List risk-status category during the period 1988 to 2012 (with two mammalian species moving in the opposite direction). The most serious threats to vertebrate pollinators in terms of the number of species affected are reported to be habitat loss caused by unsustaina-ble agriculture (seriously affecting both bird and mammalian pollinators), hunting and trapping (a threat to mammals in particular) and inva-sive alien species (a threat to birds in particular) (ibid.). Key drivers of change affecting pollinators are further discussed in Chapter 3.
Status and trends of pollinator-dependent crops A study undertaken by Aizen et al. (2009) using FAO data concluded that the global economic impor-tance of pollinator-dependent crops relative to pollinator-independent crops increased significantly Box 4.3
Monitoring total flying insect biomass over 27 years in protected areas in Germany Insects play a central role in the supply of several ecosystem
services, including pollination, biological control and nutrient cycling, and provide a food source for a wide range of species, including many birds, mammals and amphibians (Noriega et al., 2018). A decline in insect numbers therefore has serious implications for ecosystem functioning, dynamics and integrity.
Based on long-term insect-trapping results from 63 nature-protection areas in Germany, Hallmann et al.
(2017) concluded that over the period 1989 to 2016 flying-insect biomass underwent a seasonal decline of 76 percent (“seasonal” refers to the period 1 April to 30 October) and a mid-summer decline of 82 percent.
The fact that all sampling sites were within nature-protection areas makes the decline even more alarming.
The authors note that the presence of the effect
throughout the season and across all habitat types studied suggests that large-scale factors must be involved, but that analysis of data on climate, land use and local habitat characteristics indicates that changes in these factors cannot explain the decline. They mention that agricultural intensification “(e.g. pesticide usage, year-round tillage, increased use of fertilizers and frequency of agronomic measures)”, although not incorporated into their analysis, may be a plausible cause (almost all the study sites were close to agricultural fields). They also note that the effect
“must have cascading effects across trophic levels and numerous other ecosystem services.”
Following this and other similar studies, Germany initiated an Action Programme for Insect Protection (see https://www.bmu.de/insektenschutz/).
between 1961 and 2006. Yield growth and stabil-ity in pollinator-dependent crops have, however, been lower than in pollinator-independent crops (Aizen et al., 2009; IPBES, 2016a). The reasons for this have not been clearly established. However, many studies at local scales show that crop pro-duction is higher in fields with diverse and abun-dant pollinator communities than in fields with less-diverse pollinator communities (Garibaldi et al., 2016). Pollinator density and diversity depend, in turn, on the characteristics of the local environ-ment (e.g. the quality and quantity of food and nesting resources) and on management practices in agriculture. For example, Klein et al. (2007) report case studies for nine crops on four continents that indicated that agricultural intensification jeopard-izes wild-bee communities and their stabilizing effect on pollination services at the landscape scale (see Section 5.6.7 for further information on links between management practices and pollinator diversity and pollination services).
Status and trends of pollination
Countries’ responses on trends in the supply of pollination services in particular production systems are summarized in Table 4.4. In livestock grassland-based systems, reports of decreasing trends predominate. In crop, forest and mixed systems, trends are mixed (i.e. neither positive nor negative nor stable trends predominate). Some countries report perceived declines (quantitative data are generally lacking) in the state of polli-nation services in agriculture without specifying which production systems are affected.
Where explanations for reported trends are pro-vided, they often apply to more than one production system. Many countries identify the use of pesticides, human-induced habitat loss and fragmentation and climate change as major causes of declines in pollinator abundance across production systems.
Several countries report that the availability of food sources for pollinators in agricultural produc-tion systems is being jeopardized by a decline in the diversity of landscapes and plant communities.
Nepal, however, notes that crop diversification in its rainfed crop systems has increased pollination
levels. Several European countries mention that the establishment of flower strips in and around fields (incentivized through agri-environmental schemes) may have led to an increase in the number of pol-linators in surrounding areas. In the case of rainfed and irrigated crop (non-rice) systems, some coun-tries (e.g. Zambia and Switzerland) report that invasive plant species are replacing plant species that pollinators depend on for food.
With regard to grassland-based livestock systems, Zambia reports that wild pollinators are among the components of BFA that have been negatively affected by a recent decline in the number of live-stock herds (caused by disease outbreaks). Norway notes that the gradual abandonment of extensive grazing is leading to the disappearance of habi-tats that benefit pollinators. Conversely, Argentina reports that overgrazing in grassland systems is reducing pollinator habitat. Loss of habitat in natu-rally regenerated forests is reported to be affecting pollinators in a number of countries. Some coun-tries, however, mention that forest area, particu-larly planted forest area, is increasing and that this is creating habitat for pollinators. Logging and the overharvesting of non-wood forest products (specif-ically plants) are reported to be among the causes of loss of pollinator habitat in forests. Grenada mentions that natural disasters such as hurricanes have disturbed forest ecosystems, with deleterious effects on pollinators.
Several countries report that efforts to raise awareness of the importance of pollinators have had positive effects. Poland, for example, reports that growing awareness of the importance of honey bees in increasing crop yields, along with growing demand for pollination services in large plantations of insect-pollinated crops, is expected to lead to increasing interest in beekeeping and an increase in the honey bee population.