The Ecological Rationale for being Vegetarian

Choosing to eat a plant-based diet will indirectly help feed more people and it requires less resources to produce it; a vegetarian diet is more eco-friendly. Read on to find out why…

Plants start with sunlight, air and water, run it through the magical process called “photosynthesis” and presto – they have the chemicals they need to make more plants. They go about this systematically… the germinating seed throws up shots and burrow in roots, then it grows more of its own tissues and thereafter, with some help from insects, birds and animals cleverly enticed, sets out flowers, fruit and then seeds to germinate into new young plants. All parts of the plant in turn are food for some animal. Snails rasp at young stems, aphids suck sap from leaves, worms chew at the roots and caterpillars bore into fruit, all turning tissue manufactured by the plant to a new kind of tissue performing a new role in the living system.

When a plant makes a sugar molecule, it locks up in body tissue only a fraction of the energy it used to make it. And as the molecule passes on from the plant to the aphid or caterpillar that feeds on it, only a fraction of the energy is transferred to the molecule’s new host. Plants fix only about 2% to 8% of the sun’s energy in their own tissues. And each time energy is passed on from one organism to the next, no more than 10% of it is used to build new tissue. The rest may seem to be wasted, but most of it is used for warming the animal, maintaining its body functions and for moving it around.

In other words, if 100 units of energy from the sun reach the plant, a maximum of 10 units is converted to plant tissue. When this plant is eaten by an animal, only 10 % of the energy generated by what it eats (i.e 1 unit) is converted to its own tissue. When a meat-eater (or carnivore) eats this plant-eater (i.e. the herbivore), a similar process repeats… only 10 % of the energy generated by what it eats (i.e 0.1 units) is converted to its own tissue. Therefore, of the initial 100 units of energy that reached the plant, the plant tissue stored only 10 units, of which the herbivore’s body stored only 1 unit, and finally only 0.1 units of the original 100 units of energy from the sun appears as the flesh and blood of the carnivore.

What is the implication of this? For the herbivore to get 100 units of energy in its food, it needs to eat 10 plants, and still only 10 units of energy will show up as body growth. For the carnivore to get the same 100 units in its food, it needs to eat 10 herbivores. This means that for every carnivore to survive and grow there have to be 100 plants available! Note that the numbers are shown only as indicators of the trend and are not exact.

There are two implications of this…
(a) The reduction in availability of energy for conversion to body mass as one goes up on the food chain necessarily results in pyramid structure in populations – the plants at the base of food chain have the largest numbers, and the number of carnivores at the top of the chain are few. Therefore, relatively small population of tigers needs a much larger number of deer population, both of which need a much larger forest area to survive. And herbivores such as elephants which need to consume 200 kg of food per day to sustain their large body mass are migrants by nature’s design; if they don’t move on and allow time for the forests to regenerate, they can wipe out the forest in a short time!

(b) With respect to human food requirement, to produce 1 kilogram of meat, it requires 20 kilograms of grain. Therefore, meat production, particularly through commercial breeding of poultry, pigs, etc. is extremely energy intensive. Obviously, 20 kilos of grain can feed many more mouths than 1 kilo of meat. The more the number of non-vegetarians, the greater is the pressure on the environment, because, either the available grain has to be diverted to meat production or much more grain needs to be grown to produce enough meat. Diverting available grain will drive the majority – the poor – to starvation. Growing more grain implies diverting more land – obviously forest land – to intensive cultivation, use of more agro-chemicals, etc. So, if you choose to eat a diet lower on the food chain you will indirectly help feed more people and it requires less resources to produce it; a vegetarian diet is more eco-friendly.

Of course, the chain - from plant to animal to more animals – is made a circle by microscopic organisms in the soil; tiny creatures often visible only under the microscope and composed only of a single cell, yet performing a role so vital that without them life would wither overnight. These scavengers of the soil feed on the bodies of the dead, breaking down their tissues into molecules that are absorbed by the plant roots and returned to the cycle of life above the ground. All animals, including man, are a part of this cycle.

But the nutrient cycle is not driven by the life within; ultimately it is powered by the energy radiating from the sun. Only with that unlimited supply of power can the limited resources of the earth be endlessly re-circulated through the thin green skin we call the BIOSPHERE.