The disappearance of the honey bee is widely publicized, especially in Europe and North America, with colony collapse disorder observed in apiaries of the western honey bee, Apis mellifera. Much less interest, however, has been paid to Southeast Asian native honey bees whose fate also deserves attention. This article explores the conservation challenges of the eight native honey bee species of Southeast Asia.
Native honey bees in Southeast Asia
Among the nine honey bee species known worldwide, only one is native to Europe and Africa. The other eight species are native to Asia and all are present in Southeast Asia. Broadly speaking, Asian native honey bee species can be divided into three groups based on morphological criteria and the structure and location of their nests. These groups include the giant single comb open air nesting honey bees, the medium-sized multiple combs cavity nesting honey bees and the dwarf honey bees, which build small single comb nests in the open air (1).
Giant honey bees
The Asian giant honey bee, Apis dorsata F., and the Himalayan giant honey bee, Apis laboriosa S., are not only large in size, but are also distinctive by the extensive size of their colonies and the nests they build. Apis dorsata worker bees measure between 1.7 and 2 cm with colonies that count up to 80,000 bees. Their nests measure up to 1 m in height by more than 1.5 m in length (2) (3). Asian giant honey bee colonies frequently nest in dense aggregations (4) (5) and several dozen nests can be seen on the same tree or cliff (6). While Apis dorsata have a wide distribution range, covering the Indian subcontinent and Southeast Asia (7) (8), Apis laboriosa is broadly restricted to the Himalayas (9) (10). Nesting at altitudes of 1,200–3,500 m (11), this species’ presence in Southeast Asia is restricted to the mountainous areas in northern Laos, Myanmar and Vietnam.
Cavity nesting honey bees
There are four species of cavity nesting honey bees, forming the largest group of Asian honey bee species. These are: Apis cerana F., Apis koschevnikovi E., Apis nigrocincta S. and Apis nuluensis T.. Multiple combs cavity nesting bees are amenable to beekeeping. Apis cerana has the largest distribution range of all Asian honey bee species, extending west to Afghanistan, northeast to Japan and southeast to Indonesia and the Philippines. The other three species have smaller distribution ranges. Apis koschevnikovi is present in Indonesia and Malaysia, Apis nigrocincta in Indonesia and the Philippines and Apis nuluensis is endemic to the highlands of Mount Kinabalu in Borneo (9) (12).
Dwarf Honey Bees
The black dwarf bee, Apis andreniformis S., and the red dwarf bee, Apis florea F., are the smallest honey bee species in the world with worker bees of a size between 7 to 10 mm. These two species form small colonies of a few thousand bees with their nest consisting of a single comb, around 20 cm in diameter, attached to a small branch (13). Both of these dwarf species are present in most of Southeast Asia but the distribution range of Apis florea extends further west through the Indian subcontinent and up to the eastern region of the Arabian Peninsula.
Defense strategies of Asian Honey Bees
Asian honey bees have developed a range of defense strategies against predators, parasites and diseases. To deter predators, Asian honey bee colonies produce hissing sounds and perform defense body shaking at the entrance of the cavity nesting site or on the surface of the nest in the case of open air nesting species. These defensive movements are particularly impressive in the giant honey bee species, Apis dorsata and Apis laboriosa, whose worker bees’ synchronized twisting results in circular defensive waves on the surface of the nests (14). Dwarf honey bees prevent attacks by predators such as weaver ants (Oecophylla smaragdina) by coating the branch supporting the nest with propolis (15). Apis cerana uses thermal defense to neutralize predatory hornets. Known as “heat balling,” worker bees form a ball around the hornet, raise the temperature by vibrating their wing muscles until reaching a temperature that is lethal to the hornet but tolerable for the bees (16) (17) (18).
Migrations of Asian Honey Bees
Asian honey bees have the particular characteristic of moving their nest in response to seasonal changes (13) (19). These migrations remain poorly documented but it is for example known that Apis andreniformis and Apis laboriosa perform altitudinal migrations with the former nesting at higher altitude in rainy season and lower altitude in dry season (13) while the latter avoids the harsh winter conditions by migrating downhill (20) (21). Apis dorsata colonies are able to travel up to a distance of 200 km during their seasonal migrations (4).
Value of Southeast Asian native honey bees: why they should be protected?
Up to 30% of the world’s food consumption is derived from plants that depend on pollination by bees and other insects (1). Bees in particular, play a crucial role in food production through the pollination of crops (22). Since agricultural yields can be maximized, in terms of quantity and quality, by abundant and diverse populations of pollinators (23), the presence of several native honey bee species is an asset for agriculture in Southeast Asia. While some crops can be pollinated by several species, other crops are dependent on a specific bee species. The Asian giant honey bee, Apis dorsata, which has the unique ability to forage at dusk, is essential for the pollination of crops and trees which bloom at night, such as the dragon fruit (Hylocereus undatus).
Pollination by bees is also crucial to the conservation of natural ecosystems (24) (25). Fruits and seeds resulting from pollination are essential to the regeneration of the forest and various animal species depend upon plants pollinated by bees for their survival. Native honey bees are also prey to other insects, amphibians, reptiles, birds and mammals, thus playing a direct role in the overall food chain(1). Since Southeast Asian forests evolved in the presence of two or more honey bee species (25) preserving the abundance and diversity of bees is of paramount importance in maintaining and conserving balanced ecosystems in Southeast Asia. A collapse of native honey bee populations could have cascading effects on the biodiversity of Southeast Asian ecosystems.
Southeast Asian honey bees also have socio-economic and socio-cultural values. The collection of wild honey, often referred to as “honey hunting” has been practiced in Southeast Asia for more than 40,000 years (26) and is continuing to generate income for tens of thousands of honey hunters who mostly belong to the poorest communities. Wild honeys often have a better reputation than farmed honeys and are widely used in traditional medicine. The most commonly hunted species are the two giant honey bees, Apis dorsata and Apis laboriosa due to the amount of honey they are able to produce (up to 80 kg per colony for Apis laboriosa (27)) and the red dwarf honey bee, Apis florea, whose gentle behavior makes it an easy “prey”. The more defensive black dwarf honey bee, Apis andreniformis, and the less accessible cavity-nesting bees are usually less hunted due to the poorer cost-to-benefit ratio which can be measured on the basis of number of stings to the quantity of harvested honey. Where both species of giant honey bees are present, such as in northern Vietnam, honey hunters often neglect Apis dorsata, which are considered more defensive and favor collecting the honey of Apis laboriosa instead.
Additionally giant Asian honey bees, Apis dorsata, indirectly contribute to economic well-being and environmental conservation of protected forests since, in many areas of Southeast Asia, villagers are encouraged to harvest wild honey from Apis dorsata colonies in compensation for agreeing to a logging ban in compliance with non-timber forest product programs (NTFP).
Main threats for Southeast Asian honey bees
Deforestation deprives bees of nesting sites (hollow trees for cavity nesting bees, strong and high branches for Apis dorsata, shrubs for Apis florea and dense forests for Apis andreniformis) and floral resources (forest species constitute the bulk of floral resources for bees in Southeast Asia) (28) (29). The red dwarf honey bee, Apis florea, whose colonies are commonly found in anthropized ecosystems, such as agricultural or urban areas (13)(30), might be more resilient to deforestation than other bee species.
Agriculture intensification is also a major threat to native honey bee populations. Similar in impact to deforestation, large-scale monocultural agro-systems deplete the floral resources and nesting sites. Some plantations may provide abundant floral resources but only for a short period of time (31) or covering only a part of the bees’ nutritional requirements, for example only pollen in the case of palm oil and corn, or only nectar in the case of rubber trees. In addition, monocultural agro-systems often rely on heavy use of pesticides.
The impact of pesticides on Asian native honey bees is poorly documented. However it doesn’t mean that Asian native honey bees are not impacted, but rather that this impact is not monitored! Pesticides may contaminate foragers crawling over sprayed surfaces of plants or flying across treated fields. Bee colonies nesting downwind, up to hundreds of meters away, can be affected by pesticide droplets or contaminated dust particles. Notorious for their prominent role in colony collapse disorder, systemic insecticides such as neonicotinoids pose a very serious risk to bees not only because of their higher toxicity and longer persistence in the environment than most pesticides, but also because of their particular mode of action. The acute toxicity of most systemic insecticides is 3.000 times higher than the limit set up by the U.S. Environmental Protection Agency (EPA) for bee-toxic pesticides. To put this into perspective: 1 teaspoon of neonicotinoids is enough to kill 1,250,000,000 bees (32). Water-soluble and often used as coated seeds, systemic insecticides are absorbed by a plant as it grows and residues of the insecticide are present in all parts of the treated plants, including the flowers (pollen and nectar) as well as guttation drops (e.g. in the case of maize or cassava). Bees foraging on treated plants ingest the pesticide. If they do not die soon after exposure to lethal doses, they bring pesticide residues to their nest where the whole colony may be affected.
In addition, as only a small part of the insecticide is absorbed by the crop, the remaining toxins are absorbed by nearby plants or end up in local water bodies. As a result, not only the crop, but also the weeds, bushes and water bodies surrounding the cropland that was treated with systemic pesticides are contaminated.
Destructive honey hunting practices, in which villagers not only harvest the honey but cut the whole nests (honey and brood) may also put pressure on wild bee populations. Even though colonies usually survive the destruction of their nest, provided that the queen has not been killed, and rebuild a new nest a little further away, the deprivation of their food stock and brood may reduce their ability to swarm. Swarming is the honey bee colony's natural means of reproduction so a reduced swarming rate may compromise the survival of bee populations. Night harvesting, usually preferred for aggregate nests or particularly strong Apis dorsata colonies, as well as the use of insecticides or fire by inexperienced honey hunters to reduce the number of stings received, are particularly destructive as many colonies are killed (33) (34). The high demand for bee brood in some countries such as in Cambodia, contributes to encouraging unsustainable hunting practices. Without significant impact when practiced by a limited number of hunters on abundant bee populations, unsustainable honey hunting practices may become a serious threat for bee populations already weakened by deforestation and pesticide and subject to intense hunting by an increased number of hunters.
While much remains to be understood about the consequences of climate change on the western honey bee, Apis mellifera, almost nothing is known about the likely impact of climate change on the eight native Asian honey bees. Forest fires, increasing in frequency and intensity due to extended droughts and high unseasonal temperatures, are likely to impact native honey bee populations through colony destruction and the subsequent decline in swarms. Massive forest fires, such as the current Australian bushfires and the devastating fires in Brazil in 2019, could cause the extinction of local populations of native honey bees. Climates becoming wetter or drier than normal may also lead to decline in available bee forage and prolonged rainy episodes can starve bee colonies by limiting opportunities for foraging. Climate change may also modify the phenological overlap between flower blooms and honey bees migrations, leading to a deficit of food for bees and pollinators for plants.
Current status of Southeast Asian native honey bees populations
In absence of a comprehensive overview, the status of the eight native honey bees species in Southeast Asia is poorly known. However, numerous researchers, beekeepers and honey hunters have reported declines of local bee populations in recent years. Theisen-Jones & Bienefeld (35) highlighted the decline of Apis cerana throughout the whole region. Thai and Vietnamese researchers mentioned the decline of Apis Andreniformis in Thailand (36) and Vietnam (37), a species which also appears to be rare in Cambodia. Oldroyd, & Nanork (1) reported on the decline of Apis koschevnikovi in Malaysia. The Vietnamese population of Apis laboriosa has undergone a dramatic decline since its discovery in 1996 (38) (39) and Apis dorsata has also strongly declined in extended areas of Cambodia over the past two decades.
Even though none of the eight native honey bee species seem to be threatened with extinction in the short term, the pressures to which these species are locally subjected could result in local extinctions and thus call for a strengthening of measures contributing to their protection (1).
Preservation of Southeast Asian honey bees
As they are mostly forest species, Southeast Asian native honey bees will greatly benefit from forest conservation and the restoration of damaged forests, provided that protected areas take into account the migration itineraries of the bees. Protecting a particular seasonal nesting site of a species might be useless if other seasonal nesting sites are deforested. By reducing the use of pesticides and encouraging polyculture, agroecology would also play a crucial role in the restoration of native honey bees populations in the region.
Honey hunters are often receptive to ideas that may help conserve bees (1). Nondestructive honey harvesting methods, preserving the bee brood, thereby allowing multiple harvests, have been successfully introduced to Apis dorsata honey hunters communities throughout the region. These efforts should be encouraged and continued with protocols introduced to monitor populations and to ensure that the level of harvest is compatible with a sustainable management of the resource. Rafter beekeeping, a sustainable management of Apis dorsata, developed by several communities throughout Southeast Asia, could be introduced to communities unfamiliar with the method (40) (41) (42). Consumer awareness campaigns, describing the influence of bee brood consumption on destructive honey hunting practices, should be encouraged.
By providing an alternative source of income to honey hunters, beekeeping and meliponiculture (raising of stingless bees) may encourage hunters to turn away from their traditional hunting activities. As part of biodiversity conservation programs, native cavity-nesting species such as Apis cerana should be preferred over the introduced species Apis mellifera. In addition to reducing hunting pressure, sustainable beekeeping with native species, can also contribute to the restoration of the local bee populations of cavity nesting honey bees. This has been demonstrated by Apis cerana beekeepers from Oudomxai Province in Laos.
The genetic variability of Asian honey bees will very likely be crucial to their adaptation to climate change, thus preserving this variability should be regarded as a priority (43) (44) (45). From this perspective, the development of beekeeping with native cavity-nesting species, should be conducted exclusively from local ecotypes of the species (46) (47). In order to prevent competition for floral resources, large scale beekeeping with the introduced honey bee, Apis mellifera, should be banned from natural ecosystems, or minimally from protected forests.
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