‘Insects and other terrestrial arthropods ~ such as bees, butterflies, beetles, and the like ~ are so essential to ecosystems that if they were to vanish entirely, humanity might not survive for more than a few months.” — E. O. Wilson, The Diversity of Life
Plant-insect interactions encompass a wide array of relationships, ranging from the beneficial (like pollination) to the detrimental (like herbivory). These interactions are driven by a complex interplay of chemical and physical factors, that influence both plant defense mechanisms and insect feeding strategies. Through coevolution, plants and insects have developed intricate adaptations, shaping ecosystems, and impacting agriculture. The amazing partnerships support the survival and reproduction of various species and strengthen interconnectedness of life.
Pollination is one of the most fascinating processes in the natural world. The simple truth is we cannot live without pollination. Pollen, looking like insignificant yellow dust, bears a plant’s male sex cells and is a vital link in the reproductive cycle. Pollination is the process of transferring pollen from the male part of a flower (anther) to the female part (stigma), enabling fertilization and seed production.In self-pollination, pollen grains are transferred from the anther to the stigma of the same follower, another flower of the same plant.
However, pollen transfer is predominantly facilitated by wind, water, and animals, primarily insects and birds. Pollinators, in a way, are the guardians of our ecosystems. In wind pollination (also called anemophily) pollen is distributed by wind. About 12 percent of plants across the globe are pollinated by anemophily, including cereal crops like rice and corn and other prominent crop plants like wheat, rye, barley, and oats. In addition, many pines, spruces, and firs are wind pollinated. Water pollination occurs in only a few aquatic plants and is highly complicated and derived. There are nearly 200,000 different species of animals around the world that act as pollinators. Of these, about 1,000 are vertebrates such as birds, bats, and some small mammals, and the rest are invertebrates.
Flowering plants, which are primary sources of food for humans and animals, typically reproduce by delivering pollen to each other to fertilize seed. Many bird pollinated flowers are bright red, especially those pollinated by hummingbirds. These birds rely solely on nectar as their food source. Flower pollinated by birds produce copious quantities of nectar but little or no odour because birds have a very poor sense of smell. Flowers pollinated by bats produce large quantities of nectar and strong fragrance. The UN’s Food and Agriculture Organization (FAO) says bees alone, both wild and domesticated, pollinate 85 percent of all cultivated crop and a significant portion of wild-flowering plants. Bees usually feed on nectar and in some cases on pollen. They may be general pollinators by visiting flowers of any spe – cies. Without cross pollination by bees, the genetic exchanges between different plants would be restricted, impacting the pro – cess of gene flow in nature.
Thus, bees have had a very strong evolutionary connection with plants for several million years in the geological time scale. Through this systematic evolution, both bees and their host plants have arrived at the current morphological and ana to – mical characteristics necessary to facilitate pollination in nature to secure the next generation of plants. We see the bee as a honey maker. But what we fail to appreciate is how much impact bees have on our food through the pollination of crops. They play a fundamental role in the food chain. Charles Darwun described bees as “humble-bees”. As they dance from flower to flower, bees transfer pollen to fertilize plants so they can produce seeds and fruits. They spend much of their time in farmland. Highlighting the importance of the bee, Albert Einstein said: “If the bee disappears from the surface of the earth, man would have no more than four years to live.” Not just bees, but scores of other natural pollinators such as moths and butterflies; some species of flies, beetles, ants and wasps are all involved in pollination. Insect pollinators are Nature’s tiny farmers.
However, more than 87 percent flowering plant species rely on pollinators for reproduction and yields. Reliance of yields of common crops on pollinators is shown alongside in a tabular form: There are widespread rep – orts and studies indicating disappearance of pollinators at an alarming rate in many parts of the world due to both natural and anthropogenic factors: ra – pid expansion of industrial and intensive farming practices with increasing population, indiscriminate application of toxic chemical insecticides and ex – cessive uses of chemical fertilizers, air and water pollution, climate change, lack of suitable foraging plants, changes in the land use pattern and low nutritional level vis-a-vis low immunity of pollinators.
Scientists and environmentalists have been sounding an alarm on pollinator loss for decades. Indeed, we have noticed our gardens have gotten quieter, with fewer butterflies and lower hum from buzzing bees. Since 1987, the Joint Nature Conservation Committee (JNCC) has reported that pollinator numbers have decreased almost 25 percent. A study published in Current Biology in 2008, shows yields of pollinator-dependent crops have stagnated or declined,while crops not reliant on pollinators remain nearly unaffected. This crisis,termed as “Pollinator limitation”highlights the dwelling availability of pollinators and its direct threat to food security.
As a prerequisite for fertilization, pollinators are essential for the perpetuation of the vast majority of the world’s plant kingdom as well as to the production of most fruit and seed crops. Flowering plants have coevolved with their pollinator partners over millions of years producing a fascinating and interesting diversity of floral strategies and pollinator adaptation, the great variety in colour, form, and scent we see in flowers with pollinators. The various flower traits associated with different pollinators have been seen as pollination syndromes. Above all, without pollinators, the human race and the terrestrial ecosystem would not survive. Pollinators, in away, are the guardians of our ecosystems. “Our future flies on the wings of pollinators.”
(The writer is a retired IAS officer)