Animals – Okay to belch

Leafy vegetation is full of cellulose that animals like us cannot digest. If we could digest grass clippings, imagine the dent that would make in the weekly grocery bill. But many herbivores have a clever trick of providing an expanded area of their intestinal tract for friendly bacteria and protozoa that can break down cellulose to live in. Some of these break-down products can then be absorbed and used by the host animal, but there is a waste product – methane –  a greenhouse gas, which must be vented. Ruminants have huge pre-stomach areas devoted to this process. They vent their methane by belching.

In recent years agriculture has come under considerable criticism for the amount of methane farm animals belch into the atmosphere. But the problem of methane, I believe, is already mitigated by our farming system’s ability to retain carbon dioxide.

All the same, carbon dioxide (CO2) is on the increase in our post-industrialised, warming-up world. Increasing (CO2) levels in the atmosphere mean more is dissolving in the oceans too, slowly lowering their pH. CO2 is the waste product when food or fuel is burnt with oxygen to produce usable energy. In living things this process is called cellular respiration. Happily for the world, plants’ equivalent of animals eating is the process of photosynthesis where they ‘eat’ CO2 molecules from the air using energy from sunlight to form their food and structural building molecules. The waste exhaust of this process is oxygen (O2), which is not a greenhouse gas. The O2 that plants exhaust from photosynthesis is far greater than the CO2 exhausted from cellular respiration. This is the basis of carbon trading. If you are responsible for burning lots of fuel in your work, play, travel and so forth, you can buy absolution by paying for trees to be planted, which will capture the CO2 back.

Over millions of years, some of the carbon tied up in the cycle of life and death has been sequestered underground as some dead plants, animals and microbes have become coal, oil and gas. But in the last 200 years, much of that has been burnt in machines and released as CO2. This is the essence of global warming and ocean acidification. The burning of fossil fuels is the problem, not belching ruminants.

The good news is the answer is simple. We need to stop burning fossil fuels and stop growing the human population. The bad news? The good news isn’t happening any time soon.

David Haugh, Wellsford Vet Clinic
www.vetsonline.co.nz/wellsfordvet