Rice Article: Philippines
The ricefield: keeping alive the treasure trove in biodiversity
By Jose G. Burgos Jr.
Today, October 7, 2001
As the first rays of sun streak across the ricefield, an observant eye can see how balanced its ecology is: gossamer webs of spiders lull atop dense rice leaves like miniature circular hammocks; a brown-plumed bird glides then suddenly sweeps down into the rows of rice plants in search of insect-food and fallen grains; and the vibrant sounds of crickets/cicadas punctuate the awakening field.
When rains come, frogs cheerily croak their almost ceaseless chorus and below the moist earthen edges of ricebunds (pilapil), a snail now and then slowly slices through the muddied irrigation water-and in its wake, an emergent succulent leaf is devoured.
Underneath the green canopy of palay leaves, however, lies another world to complete the portrait of ricefield biodiversity: insects, both predators and prey, mingle with parasitoids and other microscopic denizens. Sometimes finny creatures like mudfish and tilapia from nearby ponds and streams slough their way into the watery sod.
Here, a lesson is being taught: if you leave the ricefield alone, you keep it alive. But disturb it with extraneous chemicals and other toxic detritus, you kill it.
Sadly, this is what's happening today in the Philippines-and in most of Asia. The mass destruction of ricefields goes on unabated either by conversion to industrial and commercial sites or residential subdivisions, on one hand, or the rampant and abusive application of pesticides and other harmful chemicals, on the other. Ricefields, according to newly acclaimed national scientist Benito S. Vergara, offer a wealth of nature's benefits. They are a microcosm of biodiversity and their conservation is as essential as other ecological communities like forests, grasslands and marshes.
Dr. Vergara, who was recognized last month for his scientific achievements on the physiology of the rice plant, points out that the area occupied by ricefields in the Philippines is 3.3 million hectares as compared to old forests (dipterocarp), 0.8 million hectares, and grasslands, 1.5 million hectares.
''Yet, we tend to ignore this rich source of biodiversity,'' Dr. Vergara laments.
The ubiquitous carabao has always been associated with ricefarms but other smaller animals are also found together with the beast of burden. These include birds, reptiles and amphibians, as well as such invertebrates as snails, shrimps, leeches and crickets. Besides these are the insects, mites, spiders and crustaceans which play a vital role in the food chain within the ricefields.
Among the birds are the wild ducks, tikling, bato-bato, tagak, maya and pipit.
According to a study by Dr. Vergara based on the ''Ecological Value of Ricefields in the Philippines,'' there are 31 bird species recorded in Philippine ricefields. Most of them feed on insects, some on invertebrates and others on residual seed grains. Seven other species of birds have been reported to migrate to the Philippines during winter in our swamps and ricefields.
Other vertebrates in ricefields are frogs, snakes, skinks (i.e., lizards), turtles, rats and snails. Of the eight rodent species found in ricefields, four are considered major pests of rice.
Reptiles and amphibians in the ricefields, however, have sustained the impoverished farmers for years.
Irrigation canals are the main source of frogs that are caught for food. In Los Baņos, Laguna alone, five species of frogs have been reported in the ricefields. But amphibian populations are dramatically declining, according to Dr. Vergara. He said that dozens of frog and salamander species are believed to have become extinct in recent years because of to ecosystem destruction. Many wetlands have been permanently drained for urban development, and this is also the fate of ricefields, an important alternative habitat for many wetland organisms, Vergara added.
Reptiles such as tuko (Gekko gecko), bubule (Mabuya multifasciata), bayawak (Varanus salvator), cobra (Najanaja philippinensis), dahong palay (Dryophis sp.), and other snakes have also been identified. Snakes, lizards, and frogs are generally predators, and since they thrive on insects, they are helpful to rice farmers.
Field rats, monitor lizards, and snakes are also sources of human food. Sawa (Python reticulata) is considered a delicacy and is used as medicine, and the skin is used for making shoes and bags.
But the source of less ''exotic'' food to the farmer are the canals and ponds teeming with fish such as dalag, hito, gurami, and lately, tilapia.
According to Vergara, large invertebrates like snails, shrimps, leeches and crickets are also important ricefield animals. Snails (Pila luzonica or kuhol) are an important food of the farmer. Unfortunately kuhol is getting rare and is being displaced by the golden apple snail (Ampullaria or Pomacea canaliculata), which has become a pest of the rice plant. It is a classic case of a perceived boon turning out to be a bane. A method of reducing the population of the golden apple snail is raising a few ducks in the ricefield. Another edible snail, but not as popular, is the pilipit (Thiara sp.).
In Pampanga mole crickets or suhong (Gryllotalpa orientalis), collected from ricefields, are a delicacy.
But the highest biodiversity among ricefield animals is found in the small invertebrates such as insects, mites, spiders and crustaceans. They play an important role in food webs as predators or natural enemies of other insects and mites, and as pests of the rice plant.
Vergara said an overwhelming number of 1,522 species have been identified in Philippine ricefields. Of these, 46 percent are predators, 32 percent herbivores or plant eaters, 16 percent parasitoids, and 6 percent scavengers/tourists. There are 306 species of Hymenopterans such as bees, wasps and ants; 303 species of predatory spiders; 272 species of beetles and weevils; and 258 species of aphids, leafhoppers and scale insects.
He said species richness is highest in the beneficial group of bees, wasps, ants and spiders that prey on the insects and mites that infest rice plants. The friendly insects constitute 63 percent compared with 32 percent grass or rice plant eaters, a 2:1 ratio of natural enemies to pests.
But, according to the rice scientist, ''human interventions or activities favor the survival of pests.'' For example, spraying of insecticides to kill the insect pests of rice also kills the friendly insects, and in a larger proportion.
The judicious use of insecticides is important if we want to keep the friendly insects dominant in ricefields, Vergara advises. In many situations, pesticides are not necessary unless there is really an epidemic, he added.
Previous studies have shown that pesticides can be harmful to people near the ricefields and even to those in areas downstream if river water is used for drinking and home use. Some animals like snails accumulate pesticides in their bodies, making them unsafe as food for ducks and human beings, according to Vergara.
Ricefields, too, harbor mosquitoes, which can be a problem in some areas. Fortunately, the most serious malaria areas are not associated with rice cultivation or ricefields. Fish and other predators are known to reduce the mosquito population in ricefields by 80 percent to 90 percent.
The dreaded linta or leeches in ricefields are also known to have medicinal value. Leeches are an important source of medicines used for heart ailments. Other animals such as earthworms may have similar undiscovered values, Vergara pointed out.
It's about time we take a second, hard look at our ricefields, Vergara said.