- Late M. Krishnan
The concept of capacity, popular among theoretically-minded conservationists today, is by no means modern and goes back to the empirical knowledge of livestock breeders. It is a logical concept, based on certain presumptions from which mathematical calculations are made cautiously, allowing various margins of safety. Reviewing my field experience of our wildlife in many different parts of India over the past 25 years and more, it seems to me that carrying capacity calculations, as now made, are capable of leading one to fallacious conclusions ( the risk in logic is always a fallacy ) and that it can be positively dangerous to place too much reliance on such reckonings in planning our wildlife conservation.
In saying this, I must make three things unmistakably clear. First, I fully appreciate the fact that informed naturalists (as opposed to armchair experts) do not think of carrying capacity calculations as infallible or irrefutable figures, but only as a method of estimating the capacity of an area to support animal populations that is more reliable than an educated guess. Second, I write exclusively with reference to India s wildlife : elsewhere, where conditions are different or more artificially sustained, such reckonings may have a more realistic value. Third, I am all for trying to gain a better knowledge of the needs of our flora and fauna - this is no biased comment on a sound, scientific method by an old-fashioned crank, but the questioning of the soundness of a method, currently very much in vogue in our country, by a scientifically educated naturalist, solely in the interests of scientific integrity.
The method now in use of determining the carrying capacity of any tract with regard to a particular wild herbivore inhabiting it, may be summed up as follows. The perimeter and area of the tract are first determined and the vegetative tracts within it assayed; then, by means of transects, samplings, or more comprehensive estimates of the vegetation, the quantity of fodder available during the leanest times of the year in this tract is calculated, and on the basis of the daily intake of each individual of the species and the total population of the species in the area, the gross daily (or periodic) requirements are arrived at. Refinements of this method are parametric calculations based on unit mass of fodder and unit mass of the species being studied in some convenient term - for instance, one metric tonne.
Carrying capacity of the wildlife protected areas is a concept
that has yet to evolve and materialise. The exercise for
determination of the carrying capacity has been done in respect
of very few National Parks and Sanctuaries. It is quite interesting
that Shri Krishnan had raised this important issue as early as 1972.
This paper would be interesting to the wildlife managers and
Another mode of estimating carrying capacity which is broader in its base and not confined to a particular species, currently in vogue in Africa and America, is the estimation of it in terms of biomass. Biomass has been defined as the weight of a population of organisms per unit area - in practical terms and in the context of this note, that would mean the total estimated weight of the herbivores of a preserve, in stock-units of 1000 kg ( or one tonne) per square mile or square kilometre, determined as closely as possible and for a specific period or particular time. This ratio, considered along with another or other similar area or areas supporting the same herbivores, gives one an objective basis for comparison.
Elaborate precautions are taken at each stage of such calculations, and contingent allowances made so as to invest the estimates with a reasonable measure of dependability. For example, what is felt to be "due allowance" may be made for infant and juvenile populations of a species during a period (the period under survey), or for births and deaths, climatic variations and aberrations and seasonal floristic changes. And what are sought to be determined from the statistics collected are not hard-and-fast figures, but only trustworthy estimations. All this sounds so eminently reasonable that one might well think that such estimates just cannot be out, or any way, far out. Such a confidence, however, is based largely on the over-all truth, but on the compelling verisimilitude of logical and logistic arguments, and the verisimilitude of the many allowances made at each stage after the basic presumptions, I question the basis originally presumed and not the subsequent, careful calculations, the fundamentals and not the superstructure with specific reference to India s wild herbivores.
My misgivings in this matter may now be set out briefly, with illustrative examples from actual field observations.
The entire question of carrying capacity arises only when artificially imposed depletions and imbalances have already upset the balance of nature in a preserve. This is provably so. Imagine an adequate tract of forest where there has been so little human interference that the flora and fauna have subsisted naturally for years: obviously, there is no need for any strenuous effort on our part, by means of elaborate assumptions and laborious calculations from the limited data at our disposal, to determine the carrying capacity of the tract- the balance of nature that has maintained itself in the area all these years can safely be trusted to look after itself.
It is only when by human occupation or exploitation of a forest that the area becomes incapable of sustaining its wildlife (especially, when human activities in it have resulted in exotics invading the forest, or when its vegetative resources have been seriously depleted by intensive grazing or plantation work) that we begin to think of carrying capacity - and to the extent to which we are willing to have faith in our calculations of carrying capacity to remedy the situation, we betray our wholesale lack of faith in the recuperative power of nature. Is it not an indisputable fact that in our country today, in no sanctuary or faunal area has nature been given a chance to recoup by the area being freed of all human demands upon it ?
To assess the carrying capacity of any sanctuary worth the name in our country and to try, by means of "controlled cropping", to limit the fauna within that calculated capacity, is a classical instance of putting the cart before the horse. Today, the tendency of many of our pundits, wherever there has been a serious upset of nature caused by human activities, is not to remove those depletory human influences but to limit the fauna to the estimated carrying capacity. Further, the tendency is to explain aberrant faunal behaviour not as a consequence of the depletive influences in the area, but as something caused by the too insufficient carrying capacity of the land! For example, the rampageous behaviour of wild elephants has been attributed to insufficient fodder in places where human activities have not only depleted the native vegetation but also rendered life insecure and constantly disturbed to the animals!
In our preserves today, few of which are free from the depletions and imbalances introduced by human activities, the vital and most urgent necessity is efficient protection and the elimination of these deleterious human influences. Until that is done, and some time has elapsed thereafter, it would be idle to compute the carrying capacity of the area and if such protection and withdrawal of adverse human influences results, as I think they must, in the wildlife settling down more or less, there would be no need for any computation.
Even after all allowances are made, the determination of carrying capacity depends on the presumption that a determinable population of several species of animals inhabits a known area for a period (say, a year) and that they feed efficiently on the available fodder. Every field naturalist knows that this is not so - and, fortunately, cannot be so, for otherwise our natural flora, which is as integral part of our wildlife as the fauna, would have disappeared long ago.
Actually, most herbivores require a considerable range, even the less far-ranging of them like cheetal and sambar (X gaur and elephants). While it is true that within a large tract their feeding is conditioned by the availability of the best feeding locations (which keep changing with seasonal floristic and other changes), it is also time that they do not make the most efficient and intensive use of all such grounds, and that many other factors also conditioned their feeding.
In India, wild elephants in herds do not stay in the same area for any length of time. They arrive at a forest, and depart from it, mainly along the well known elephant walks which are their established tribal travel routes (and not merely the routes followed by particular herds) - though, where they are much harassed by humanity, they may leave these old trails and shift "to fresh fields and new pastures" near human habitations which were originally part of the elephant country. Another herd may have preceded a herd feeding in an area, or may succeed it there; when feeding, a large herd breaks up into parties and members of each party keep together, but the parties themselves separate (though they reunite periodically), and leave sizeable areas of rich vegetation untouched in the course of their traverse of a feeding ground - their feeding is extensive and somewhat haphazard, and not intensive. Further, elephants, where free from human disturbances feed most economically, and only when near-human presence panics them, do they lay waste to entire fields, trampling down much more than they eat. Such rampageous behaviour and general aggressiveness towards man and his artifacts is the direct consequence of human usurpation of the immemorial homes of elephants, the constant disturbance and harassment caused by men, and the blocking up of their age-long travel routes by human agriculture and holdings. It has been estimated that an adult elephant consumes about 200kg, of green fodder everyday : a herd with 20 adults in it would need, on this reckoning, no less than 4 tonnes a day, and in a month would demolish an entire forest. How is it, then, that at no time in the history of this ancient land has any single tract of forest been denuded by large herbivores such as elephants and gaur, when men have laid waste to a hundred square miles of forest within 2 years?
Before answering this question, I must firmly scotch the wholly misconceived claims of some men who say that wild elephants have laid waste to forest tracts in recent years. Where men have invaded elephant forests extensively and intensively (as in the Moyar-Masunagudi area of the Mudumalai sanctuary and the periphery of the Perivar sanctuary), constantly disturbing the great beasts and blocking up their walks , elephants do indulge in destructive activity, in their frustration, perplexity and panic. The fact remains that in the course of countless centuries not one acre of natural forest has been destroyed or depleted beyond redemption to its pristine luxuriance by wild elephants in India.
This is so because elephants feed extensively and somewhat at random, as already said, and it is no less so because their normal fodder is made up of renewable and annually renewed plant parts such as twigs and leaves, the aerial shoots of tall grasses and bamboos, fruits and even bark that is, surprisingly, renewed (as in the case of Kydla calicina). If elephants and gaur did not range far and shift feeding grounds periodically, and if the regeneration of the plants they feed on is not so much quicker than our computations suggest, so many forests would certainly have been destroyed by them - as they have been by men.
Furthermore, although they are the largest of land animals and send most of their waking time feeding (elephants, unlike ruminants, feed slowly and continually, and not in intensive bursts) elephants do no always eat the most luxuriant or nutritious bulk fodder available. I have seen wild elephants laboriously gathering the minute, pink flowers of Mimasa pudica, spending ten minutes to get a tiny morsel in their trunk-tips. It is not only elephants that behave like this. Experienced naturalists know perfectly well that at times herbivores are not to be found where the vegetation is lush and rich, but in areas where what there is, needs to be sought and found laboriously. Sambar, for instance, spend days, nibbling at the 6-inch-high sprouts of up-and-coming grass in the black, fire-charred floor of deciduous hill-forests in February, when a little farther down there is fresh green fodder in bulk.
We should know much more about the feeding habits and gustatory preferences of our herbivores (whether such preferences are induced by seasonal vegetative changes, or by the compulsion of consciously ununderstood bodily needs) before we can afford to compute their needs. Everyone knows that at times elephants ingest the basal portions of the sheaves of dusted grass they place crosswise in their mouths, and at times the distal green blades, sometimes rejecting the blades and sometimes the stalk (clums) : one might conclude, logically that it is a question of whether the green blades are fresh and comparatively free from silica, and whether the clums are starch-rich, that decides their preference in this matter. After having closely studies the portions of the sheaves that elephants reject in the course of such feeding, and also the clumps of grasses in their feeding grou nds. I am sure it is difficult for a man to know what exactly guides their preferences - unless he were a grass-eater.
Some forest fruits are avidly eaten by most herbivores when in season, such as ber (Zizyphus sp.), Grewia spp., Diospyros spp., Gmelima arborea and many legumes. The power of these trees and shurbs (and of many herbs, too) attract herbivores when they are in fruits, is seldom taken into reckoning in computing carrying capacity.
When the sour drupes of Spondias mangifera are ripe, and when Melia composita is in bitter fruit, muntjac are drawn irresistibly to the trees; the fruit of Terminalia bellerica attracts sambar, and all dear love the round fruits of Randia dumetorum, noxious to man (even Randia uliginosa has to be sliced thin, washed carefully and then boiled to be fit for human consumption). There are, of course, a great many more fruits, and even flowers, that attract many animals and even jungle- living humanity. Is all this taken into account in reckoning carrying capacity, and in delimiting the periphery of the range of animals in an area?
Even if allowances were made painstakingly, for all such known attractions, they may not always be realistic. I have seen a hill-forest carpeted 6-inch deep with bamboo seed, with not even a junglefowl attracted to the feast. The weevils had taken over.
The reverse of such factors, not attraction but repellence, is much more important in assessments of faunal life. This has not even been thought of in the concept of carrying capacity. There are exaggerated notions about the power of the dhole (wild dog) to drive away all other animals when they enter a faunal area, but even taking legend at face value, the dhole is certainly a long way behind man in the power to scare away forest animals. Wild animals just cannot stand men on foot (in India) and where noble sports-men hunt them from jeeps with searchlights, they are terrified of motor vehicles, too. In areas where there is much hunting and poaching, or where these were major factors affecting the fauna till recently, such as in Orissa, Andhra Pradesh, parts of Bihar and parts of Uttar Pradesh, even animals that are largely diurnal where they are not disturbed, like cheetal, sambar, and gaur, have turned into fugitive creatures of the night that flee at the sight or smell of man, and shelter in cover all day, coming out only with dusk and retreating into cover at dawn. Even otherwise, cover is one of the primary requirements of most wild animals, and when sheltering in cover they do not feed much - eve where the cover is edible, their retreat and feeding urges and behaviour are different. Has this vitally important factor, cover, been taken into consideration in reckoning the carrying capacity?
I may end this by repeating what is really important in wildlife conservation in India. It is not the management technique today but protection from every kind of hunting, and depletive human influences whether or not these are intended.
(Reproduced from 'Cheetal' Vol. XV-1972-No.2)