SavingSpecies understands your need to be carbon neutral. We believe there is a unique opportunity to both save species and to absorb carbon emissions. You, or perhaps an organization you represent, may be bothered by how much carbon dioxide you emit each year. Or, you may feel tortured because you’re about to go on an ecotour and worry about how much more pollution you will create by doing so.

There are many ways to save energy and emit less carbon! We’re not the place to provide that advice. But what if you’ve done all you can? An increasing number of individuals as well as organizations (including some universities) would like to become “carbon neutral.” That is, in addition to reducing our use of fossil fuels by becoming more efficient, we should protect deforested lands — particularly in the tropics — and allow the forest to grow back. Carefully selected areas would have an immediate impact on protecting threatened species while helping nature soak up carbon dioxide.

The projects we recommend will tell you exactly how much carbon.

How much degraded land could be restored?

About 5 million km2, almost as much land as now remains in tropical forest, has been cleared. It is used, if at all, as very poor grazing land. (Another 2 million km2 has become croplands — and these would likely be too expensive to reclaim.) A global map of where forest has been cleared is in Pimm and Jenkins 2005, Scientific American and shown in the next section.

However one might quibble with these maps and numbers, there is simply no doubt that there is a huge amount of land, much of it in the tropics, that is bad land or, at best, land that is used to support only low densities of grazing animals.

How much carbon would this land sequester?

When forests grow they sequester — henceforth “soak up” carbon. This is a very inexact science. Forests in warm, wet places — including temperate forests in the USA that are only seasonally warm — hold something between 100 and 300 tons of carbon per hectare.

If this has already become too technical, please skip to “Can I have a simple answer, please?” below.

To convert this to biomass, one multiplies by 2.2. To convert carbon to carbon dioxide — one adds two parts oxygen, weighing in at 8 each to the carbon weighing in at 6, that is, one multiplies by (22/6). This matters because different papers report very different units (carbon, biomass, carbon dioxide) and then further mess things up by using grams, kilograms, megagrams (which are totally inexcusable, since a megagram is a ton), and Gigatons (billions of tons), and so on.

There’s also carbon in the soil — potentially a lot of it — and those numbers are even more sketchy, especially for tropical forests, which often have thin soils.

Now, there is a debate about whether mature forests continue to store carbon. But SavingSpecies recommends land that is deforested and that, if left to grow into mature forest, would soak up carbon for years to come. Which begs the question: how many years?

How quickly does deforested land soak up carbon?

Again, the answer is quite variable, but the warm, wet places that interest us do a lot better than cold or dry ones. To demonstrate the point, take your houseplants (which are likely from the tropics) outside in winter or fail to water them and witness how much their growth varies.)

The numbers range from about 3 to 10 tons (carbon) per hectare per year.

Dividing these into the amounts of carbon held, one sees that forests should take about 30 years to recover — which strikes me as being about right, being old enough now to have watched forests grow up on abandoned land. Forests older than this will continue to grow larger trees, but trees may become more wildly spaced as smaller trees die, so whether the amount of wood increases is not entirely obvious. (And it isn’t obvious in the scientific results either.)

My name is … and I have sinned.

So, not to put too fine a point on it: how much is your carbon “sin”? The USA puts about 1.6 Gigatons of carbon into the atmosphere as carbon dioxide. That works out to be 5 tons for you, me, and everyone else. I have sinned more than most because I travel to a lot of tropical forests. If you live outside the USA, you likely sin less.

Can I have the simple answer please?

Buy just one area of regenerating forest that’s 200 yards by 100 yards and you will be carbon neutral for the next 30 years.

(That’s being really quite conservative. The area is about 1.9 hectares, which will mean that you’re soaking up somewhere between under 6 to 19 tons of carbon per year.)

SavingSpecies still encourages you to use your energy-efficient car sparingly, turn off the lights when you’re not using them, and the rest of it.

Simply, becoming carbon neutral is possible. And you can sustain the variety of life at the same time.