India Environment Portal Knowledge for change

Who will play Cupid?

• 14/08/1998

The Broken Arrows
The relationships between plants and pollinators took thousands of years to develop. Human intervention has destroyed them in a very short period. Pollinator decline is also affecting the harvest. Therefore, it is vital to conserve them, but research in this field is lacking in India

THERE are some quarter million flowering plant species on our planet. More than 80 per cent of them undergo pollination to produce seeds or bear fruit. Fertilisation is impossible without pollination. And though plants on the lower rungs of the evolutionary ladder, such as mosses and lichens, can propagate on their own, one in every three kinds of food crop needs help.

Pollination occurs when pollen is transferred from the male sex organ of the flower, the anther, to the female organ, the stigma. In most plants, certain external agents - insects, birds, animals, and in some cases, even wind and water help in this transfer. They are the pollinators or pollinating agents.

There are an estimated 120,000-200,000 invertebrate and vertebrate species that act as pollinators. Invertebrates such as honey bees, for instance, are credited for the pollination of some 100-150 major crops grown in the US, while vertebrates such as bats, hummingbirds, monkeys and many other animals and bird species are known for their roles as pollinators in different regions of the world. Together, they are crucial for maintaining plant biodiversity and boosting crop production.

Of the 1,330 cultivated crop species, including fruits, vegetables, beans, coffee and tea in the world, almost all require pollinators. "In tropical rainforests, a great deal of the biological diversity is caused by co-evolutionary relationship between the pollinating agents and the flowers that produce the seeds," says tropical biologist Scott Mori, of the New York Botanical Garden. "These relationships took thousands of years to develop. Man can come in and, in a very short period of time, destroy all these relationships."

So when, during the last few years, biologists and plant experts noticed a marked decline in the number of pollinators across the globe, there was cause for concern. Pollinator losses have not only affected the quantity of the harvest, but its quality as well. Eradicate the pollinators, says one botanist, and "the trees become living fossils". Unless this decline is checked soon, there will be severe implications on agriculture causing frequent crop failures worldwide, leading to famines in the not-so-distant future.

Despite their importance to agriculture, pollinator management is virtually unheard of in India. It is the Khadi and Village Industries Commission and not the ministry of agriculture that has a research institute - the only one of its kind - in the nation. Other developing countries such as China, Argentina and Mexico, for instance, are far ahead with more bee colonies and increased profits from apiary products.

Downward Spiral
We have witnessed a drastic decline in many pollinator species in the recent years. Number of pollinators, both vertebrates and invertebrates, are gradually going down. Some of them face the threat of extinction

• Of all the various species that play pollinator roles, bees have been the most well documented, possibly due to their role in honey production. Carry P Nabhan of the Arizona Desert Museum, USA, records a 70 per cent decline in Arizona"s wild honey bees, important pollinators in the region, since 1991. Honey bee colonies, he estimates, have dwindled to half their initial strength in the last 50 years, with majority of the losses occurring in the last five years.

• European honey bees, both managed and wild, are experiencing major population declines throughout the US and other nations such as France and Germany. In the US, for instance, colony numbers have plummeted from 2.5 million in 1995 to 1.9 million in just one year. And though the numbers of wild bee colonies are available only regionally, drastic losses are known to have occurred.

• Uma Shankar, Krishnappa Chandrashekhar and Bharat Malik, entomologists from the University of Agricultural Sciences, Bangalore, India, report a 90 per cent decline in the native Apis cerana bee populations owing to the Thai sac brood disease. The disease has wiped out substantial bee populations in Andhra Pradesh, Tamil Nadu and Kerala.

• Several other invertebrate pollinators, such as moths, wasps and butterflies, have also suffered serious decline in their populations in certain regions of the world. The exact extent of the decline, however, remains unknown owing to lack of proper documentation.

• At least 45 species of bats, including nine that are thought to be extinct, are of global conservation concern. Extinction looms large for bats in Australia, Africa, North, Latin and Central America and Asia. Fruit bats and flying foxes restricted to islands and archipelagos, have suffered the most. These areas happen to be the places where other pollinators are scarce or absent.

• Thirty-six species of non-flying mammal pollinators such as lemurs, monkeys, olingos, kinkajous and tree squirrels may be at risk of extinction in the wild due to large-scale forest destruction, habitat fragmentation, changes in canopy structure and hunting.

The black-and-white ruffed lemur, an endangered subspecies of lemur in Madagascar, is perhaps the only vertebrate with enough strength and agility to open the bracts of Ravenula Madagascarencis (traveller"s tree) to effect pollination. There has been such drastic decline in its populations in the recent years that protection of its habitat is now the topmost priority of the Species Survival Commission of the World Conservation Union (IUCN).

• Hummingbirds, essential for the survival and reproduction of many plant species, are facing a severe threat to their existence today. Owing to habitat destruction, avian malaria and other influences, this bird has become locally extirpated or threatened. As many as 26 species of humming-birds face the threat of extinction and are the cause of major worldwide conservation concern. At least seven other species of sunbirds that pollinate plants in tropical and subtropical forests are also at risk.

• Australian, Indonesian, Micronesian and Polynesian hovering birds have been classified as endangered after large-scale habitat destruction and disruption of trap-lines and their migratory routes or nectar corridors.

• Other bird species, such as finches, vireos, white-eyes and many other perching bird species, play important roles as pollinators for many flowering plants. The IUCN lists over 70 species of perching birds that play important pollinator roles as either threatened, endangered or probably extinct.

• In India, role of birds as possible pollinators was identified in 1932 by eminent ornithologist, the late Salim Ali. Since then, however, very little research has been done on avian pollinators in India. And though experts such as Asad Rahmani, director, Bombay Natural History Society, Mumbai, say that populations of pollinator bird species have gone down in the recent years, supporting statistical data is not available.

• The IUCN predicts a global loss of over 20,000 flowering plants within the next few decades. This, undoubtedly, will have severe effects on the co-dependent pollinators who need them for survival, leading to a substantial decline in their numbers.

Poisoned and Persecuted
Rampant use of pesticides, loss of habitat, rapid urbanisation and the introduction of alien species are major causes of pollinator decline

URAWA City, outskirts of Tokyo, Japan. Here, a population of rare primroses survives on a tiny floodplain reserve - 4 hectares (ha) of remnant grassland closed on all sides by an urban concrete jungle. In recent years, these lowland floodplain habitats have been completely destroyed. The result, as botanist Izumi Washitani recently discovered, is that the native bumble bees that once used to pollinate the primrose can no longer disperse there naturally. At the height of the flowering season, the roses bloomed, but in vain. Washitani observed 68 flowers for more than 16 hours. The flowers did not receive a single insect visitor. Urban development has destroyed all nearby nests, eliminating the bumblebees from the reserve, she says.

Then there is the case of monarch butterflies, pollinators native to the US. For most of their life cycle, their range is nearly the entire length and breadth of the country. However, in winters, during the well-known monarch migrations, the butterflies fly all the way down to coastal California and to the slopes of Michoacan, Mexico. In central Mexico, less than 40 ha are suitable for monarch use as wintering roots. Lepidopterist William Calvert estimated that in the winter of 1995, over 30 million butterflies were concentrated in an area little more than 5 ha. In California, 21 sites known for monarch visitations have been destroyed, either due to farming, logging or overgrazing. Seven of the remaining 15 have been damaged severely by land developers. Result: monarch populations are going down. Populations of bats, hummingbirds and many non-flying pollinators such as lemurs, monkeys and squirrels are experiencing drastic declines today due to fragmentation and degradation of habitat, a problem also faced by bees, butterflies, moths and many invertebrate pollinators.

Unplanned use of pesticides is another significant cause of pollinator decline. Pesticides sprayed to finish off agricultural pests do not spare the useful pollinators. And one pollinator that has been severely affected is the bee. Pesticides such as aldrin, malathion D and methomyl D, used against insect, pests, are the poisons killing honeybees and other pollinators in several countries, including India. Cotton, a crop that claims about 44.5 per cent of total pesticides in India, has emerged as the bees" biggest foe. Entomologists encourage frequent use of pesticides to control cotton pests, careless to the" fact that this kills off honeybees and other valuable pollinator in species. "During the pest attack that hit the cotton growers of "Andhra Pradesh, not a single bird could be seen, all due to the rampant use of pesticides," says G C Tiwari, principal scientist at the Indian Council of Agricultural Research, New Delhi.

In Bihar, for instance, pesticides used extensively on litchi and mango, two fruit crops frequented by honeybees, effectively eliminates the helpful pollinators, according to L R Verma, International Centre for Integrated Mountain Development, Kathmandu, Nepal. Carry Nabhan of the Arizona Desert Museum, USA, cites similar cases in Mexico. Sphinx moths, main pollinators for cereus cacti, are poisoned by pesticides. In many regions, pesticides are sprayed during daylight hours, when the pollinators are most active. The US Environment Protection Agency and the US Fish and Wildlife Service have set "spraying setback distances" to give valuable pollinators a margin of safety. But often, these distances are determined without referring to the actual biology on the ground, Nabhan argues.

Changes in gene pool among bee species and replacement of one species by another, therefore, have also led to pollinator decline. In the US, for instance, the European honeybee was replaced by the volatile and aggressive Africanised hybrid bees. While many native plants failed to adapt to this alien bee species, the European honeybee, a universal pollinator, was driven away as the hybrid species took over their hives. Himalayan region, known for populations of Himalayan native bee, Apis cerana, the Indian equivalent of the European honeybee, has a similar tale to tell. The main threat to Apis cerana comes from the exotic and more prolific Apis mellifera, its replacement. Apis cerana enjoys a distinct edge over its more exotic competitor, the Apis mellifera, as far as pollination is concerned. They can forage longer, begin foraging early, have short flying range, are cheaper to maintain and are best suited for the native plants. Some of them are resistant to Thai sacbood virus, a trait lacking in their exotic counterpart. Further, Varroa jacobsinii, a parasitic mite that can coexist with Apis cerana causing no serious damage is turning serious pests in Apis mellifera. To make matters worse, Apis mellifera^ an extremely aggressive species, has caused significant declines in the Apis, cerana population. The net result: overall pollinator decline.

Boosting Productivity
Even though agricultural productivity has increased worldwide, pollinators can still give it a further boost

POLLINATORS hold the key to boosting agricultural output, even more so than chemical fertilisers and pesticides. Sadly they are being neglected. If the pollinators disappear, plants die. And if plants die out, the pollinators are threatened. Judith Bronstein of the University of Arizona, USA, offers figs as an example. Each of the 740 fig species on our planet has its own tiny species of fig wasp. Yet these highly-specialised plants, she points out, are also regarded as keystones of the tropical forests because so many other animals rely on them: the monkeys that eat their fruit, "If you pulled out the keystones," she says, through a sudden loss in the plants" numbers; or perhaps pesticides wiped out the fig wasps, "the result would be an enormous and disastrous domino effect." Similarly, in Sonoran Desert in Texas, USA, for instance, 75 per cent of tremendously-varied bee species pollinate only a handful of plant species. Most of the bees service a limited number of different plants that flower in sequence throughout the growing season. If even one of these plant species dies out, the bees will be endangered.

As mentioned, the Earth boasts of some 1,330 cultivated crop species, most of which require pollinators. The consequences of pollinator decline, therefore, could be more than severe, some nations already know. The US, for instance, suffered major losses three years ago when, due to lack of pollinators and adverse weather conditions, the nation registered significant decline in its almond yield. The same year, in New Brunswick, USA, unplanned pesticide use led to a substantial reduction of pollinators and caused a 75 per cent loss in the blueberry crop production. Translated into economics, that meant a multi-million dollar setback. There are numerous other instances of how absence of pollinators have led to massive crop failures across the planet. Cashew nut failures in north Borneo have occurred after this nut species was moved from its native habitat in Brazil, without a native pollinator to assist in pollination. A mite attack in Ontario, Canada, that affected regional pollinators, caused cherry prices to sky-rocket. And that pollinator declines have been a central cause of failures of alfalfa, apples, cranberries, pears, pumpkins, cucumbers and many other fruit and vegetable crops world-wide, is known to every biologist and agricultural expert.

The resultant economics of such losses can shock any government. The value of the wild pollinators alone, to a nation such as the US has been estimated at an astronomical US $4 billion. Economist Lawrence Southwick and his brother insect psychologist Edward, calculate that if pollinators such as honeybees were to decline at the current rate, they would drop by 50 per cent in the US and by 100 per cent in the Latin America. The consequential economic impact on more than 60 US crops would reach billions of dollars annually. And if no replacement pollinators are found, the country would likely be losing anywhere between US $5.7 and US $8.3 billion every year.

How a decline in the populations of most vertebrate pollinators might affect agriculture remains largely uncertain due to lack of proper studies. Bats, for instance, are important pollinators in the tropics, deserts, and many oceanic islands. In the arid regions of the North and Latin America, they pollinate most species of columnar cacti and many agave species, while on the island of Samoa, they pollinate the majority of the dominant rainforest canopy trees. Durians, neem trees, wild bananas, timber species of eucalyptus, several species of palms and other plants of economic value are mostly bat-pollinated. A decline in their numbers would inevitably cause an imbalance in the regional biodiversity perhaps leading to a gradual extinction of these plant species, a vivid scenario, possible anywhere a pollinator species disappears.

Swarm of Plenty
If used wisely, pollinators can perform miracles. Experiments in Punjab and Malaysia have shown a major increase in the productivity of palm oil and sunflower seed

IN 1892, the US Department of Agriculture received a complaint that over 22,000 Barlett pear trees in Virginia have failed to bear fruit. The department sent its specialist who discovered that bees, the native pollinators, were wholly absent in the area. Since then, bee-keeping has become a very lucrative business for many in the US. A honeybee colony comprising, at its peak strength, some 20,000-80,000 bees depending on the species, can accurately forage on fields 30-35 sq km around the hive. These tiny wonders, Apis indica and Apis mellifera for instance, are workaholics and are not crop-specific: they can pollinate a wide variety of crop species. Endowed with branched hairs that trap millions of pollen grains, these bees make up a formidable pollinating force, hardly rivalled by any other pollinator. Today, in the US, trucks carrying thousands of beehives over long distances is a common sight. Bee-keepers rent their hives for substantial payments to agriculturists during flowering time. An estimated one million bee hives change hands temporarily during this season in the country every year.

If used intelligently, pollinators can work miracles, as Malaysia found out. Here, despite the importance of oil palms, means of its pollination attracted little official attention till 1979. The pollinator most suited for these palms was found to be the weevil (Elaeidobius kamerunicus). It was brought from West Africa and introduced in Malaysia in 1981. The weevil immediately established itself comfortably and spread rapidly throughout the country, leading to millions of dollars in profit. Today, Malaysia is the global leader in both the production - 58 per cent of world output - and 78 per cent of total export of palm oil. At home, Punjab, too, experienced a bit of the pollinator miracle. The state boasts of densest bee population and here, through the enthusiasm of the bee-keepers, the production of sunflower crop has gone up tremendously. And today, the yield per hectare of this crop in Punjab is almost 300 per cent of the national average, a performance not equalled by any other crop, not even rice or wheat for the high productivity of which this state is known.

In the 1960s, the eminent Indian cytogeneticist and bee expert, late G B Deodikar said that bee keeping has the potential to raise resources equal to the revenues of the Indian Railways. Back then, he was only referring to the benefits arising from pollinator roles of the bees, and left out profits earned from honey and other apiary products. Between 1970 and 1976, the National Commission of Agriculture (NCA) recommended that every Indian agricultural university - there are 33 of them right now, including the recognised Indian universities - should develop a section on apiculture under their entomology division for research, education and training. This, if implemented, would have had greatly accelerated apicultural development and led to agricultural prosperity. More than two decades later, nothing has been done along the lines of the NCA recommendations. Today, less than a handful of universities are actually engaged in pollinator research, and those that do only concentrate on bees.

The NCA drew up an ambitious plan to extend apiculture over the length and breadth of our nation. Every single village in the country that grew crops would have, on an average, 10 bee hives. This, the NCA predicted, would ensure bee activity on a nationwide scale and would increase the number of beehives from 0.5 million in 1976 to over six million by the end of this century. This would greatly enhance the production of apiary products and revolutionise agricultural output.

The commission, on the basis of experiments conducted in India and abroad, also predicted an astonishing increase in the productivity of most commercial crops (see table: The buzz-word). However impressive these predictions and plans might have been, nothing was to done in the following 22 years to implement them. While countries such as the US and even Malaysia have increased yields by introducing pollinating agents like honey and other bees, India is yet to realise their potential in increasing crop yield. Bee-keeping - a simple and inexpensive way of increasing agricultural production in an environmentally-friendly manner and boost rural earnings - is being ignored in our country.

M S Swaminathan, former director-general of the Indian Council of Agricultural Research, began an All India Coordinated Project on Apiculture. But this, he says, was abandoned shortly afterwards. An important eco-friendly and inexpensive way to increase production is being completely ignored, he feels. "And I don"t know why."

There are some solutions that, if implemented, can arrest pollinator decline. Strong conservation measures for endangered pollinators is a move that has to be taken to arrest pollinator decline. Conservation measures for bees, for instance, have to be implemented as widely as possible. There is a need to protect the pollinators by enacting laws that forbid all activities that might affect them. Poland, for instance, did this in 1990 when it passed laws protecting some 443 species of insects including the native bees. Experts, however, think that such laws, passed against practices that harm pollinators, will not be very effective. They point out that laws to protect the tigers and elephants have not made any significant difference in their numbers. Conservation moves should also include careful studies of the effects of pesticides on pollinators and on their habitat. Those that are found dangerous for pollinators should be banned. Migratory routes and nectar corridors of the pollinators should be protected. Authorities should carefully asses the threat from any development project that has been sanctioned.

Experts also stresses that pollinator replacement should be undertaken only after substantial research to avoid scenarios that have been faced by the US and India. The Himalayan native bee was replaced by a more exotic and volatile bee species, even though-the native species was perfectly suited for the region"s biodiversity. The result: populations of the native species declined drastically, while the alien species failed to do anything spectacular to pollination or crop production figures. Nature reserves designed specially with plant-pollinator relationships in mind can be an important step towards arresting pollinator decline. Possibly the only wild bee reserve in the world, the Lomas Barbudal Reserve in Costa Rica was set up in the early 1980s with assistance from the University of California in Berkley, USA, and has been designed to protect a community of a dozen wild bee species, which pollinate the native legume trees of the area.

These are solutions experts recommend if we are to stop pollinator decline. But these apply to only a handful of species, bees being the most prominent of these. The primary reason for this is the lack of proper and extensive studies on other pollinator species, such as bats, hummingbirds and other vertebrate and non-flying mammals. So almost all experts agree that more research on pollinators and the decline in their populations should be encouraged by governments worldwide, since this is the first of a series of steps that we must take if we want to avoid further losses and save the pollinators from extinction.

• Tags:
  • Plant Breeding
  • Endangered Species
  • Birds
  • Insects

Related Content

• The common root