Is it OK to burn?

I want to clear a large parcel of land in a wet tropical area to get it ready for agroforestry planting. It’s too large for hand-clearing.

I’ve heard arguments for and against burning vs. land clearing with heavy machinery like 30ton bulldozers. The pro is that burning is quick, inexpensive and organic.

Clearing with machines is costly and one can’t ignore fossil fuel pollution. Both methods pollute.
Machines can cause soil compaction as well as inversión of soil layers, whereas fire does not.

But I heard that fire can deplete nutrients and permanently change clay to stop absorbing water.

Yet I’ve also heard that trees planted near burned pasture grow quicker and greener than planted in adjacent non-burned areas.

Anyone have any science to help in making a decision?

Hello Windy,

Really need more information but at face value:

I suggest burning is very detrimental and destructive. Hopefully you're not clearing virgin rainforest?!

It's the sledgehammer approach often used in Third World countries with very dodgy laws and enforcement practices.

Importantly, how would you control a fire and stop it spreading to neighbouring lands? If a fire reaches the canopy, good luck.

Besides releasing huge volumes of greenhouse gases and other pollutants, it wipes out all manner of species that would otherwise be beneficial. The carbon and nutrients created by burning only last a short time - there's a lot of information on the web regarding this e.g. Rainforest clearing for palm plantations, etc

Although a PITA to do, selective clearing is by far more acceptable. That would normally involve a small number of people, chainsaws, and some vehicle/animal capable of dragging logs out.

A description of the property and your intentions would assist in further feedback.

Something to consider with burning is the soil itself and what fire does to it. Especially in rainforest jungle where the soil tends to be pretty fragile.

Here is a great video explaining the soil issue.



Link here since it is a video that is over an hour https://www.youtube.com/watch?v=xzthQyMaQaQ

When you burn you are likely to damage or even completely eliminate the fungi and other life in the soil. This turns good soil into inert dirt. It has to then be recolonized by fungi, protozoa, bacteria. This can take a long time, and generally you will not get the same diversity that was once there.

I understand you likely want to hear burning is fine, but really it is not the best way to treat the land you are looking at clearing. Limited burning can be ok, or burns that don't get too hot (sterilizing the soil with heat). But from the sounds of what your wanting to do, it would likely be pretty destructive to the soil health of the area. This means that the soil would then be stripped quickly of nutrients by anything you plant in.

People around here like to make huge piles of trees and burn them.  You can see the burn scars for years afterward. People wait until it rains and then rush out to set their piles on fire.  If it's wet enough, the big ugly piles just smolder for weeks, stinking up the whole valley and making it hard for people like me to breathe.

Burning is also really hard on any critters that happen to be living in the piles.

Context matters a lot for these types of questions. Burning around these parts, which is a fire-adapted conifer forest, is extremely beneficial. The ashes help clear out undergrowth (allowing more sun to the soil), clear out pine duff mulch (allowing more seeds to germinate), the ashes sweeten the soil opening up room for succession species (building more soil and root mass), and stratify fire-adapted seeds (resulting in an increase of fire-adapted species). But this entire ecosystem is built on fire.

One of the key differences in fire-adapted temperate climates to wet tropical areas is where the nutrients are store in the soil. Here, they are stored deeper in the soils — in decaying root mass and other forms of life. In the wet tropics, it is often stored in a dense, thin layer sitting right on the surface. Organic matter never gets a chance to be incorporated deep into the soil, it just decays on the surface. That's one of the reasons fires are so destructive in the tropics — that thin top layer of soil is easily destroyed by a low intensity fire.

Permaculture mimics nature.

Fires commonly occur in nature.

Therefore, fires is an important part of permaculture.  

In nature when people are not artificially suppressing forest fires, the fire moves through forests and clear out undergrowth and weed trees.  In a sense, Douglas Fir are one of those weed trees, but one that we've mass planted because it's quick growing and highly productive for lumber.  But we don't let fires burn through our Doug Fir forests anymore --- too much money at stake.

Most burns generally don't get so hot as to damage the soil.  The fire tends to move along the ground and clean up the biomass that sits on the surface.  But when underbrush accumulates for decades and decades, those fires burn so hot that they do significant damage to the soil.d

I use fire as a tool in land clearing, but I do not live in the tropics either.

For me, it is a combination of using heavy equipment and then burning the resulting stump piles to reduce the volume of them. At other times I have a ravine that I can fill with stumps and get rid of them that way like on a mountainside pasture project I did a few years ago. At other times burning stumps just is not possible and I must push the stumps all the way across the field to the woods line. It is all very site dependent.

(As a side note, I clear land from forest into field on my own land, as well as for others)

I'm going to come down on the side of "no". Uncontrolled burning such as you describe is hugely polluting - dense smoke, that lingers and spreads over huge areas. Those particulates are far more harmful to the atmosphere than the small amounts of fossil fuels that may be needed to get equipment in.

On the other hand, when managed under carefully controlled conditions, you could use all that material to produce biochar. Biochar when added to soils acts as a nutrient sponge, and allows your soils to store more nutrients. This is a serious issue in tropical areas, where disturbed soils are quickly rendered infertile by leeching by rainwater. I would view that standing plant material as a valuable resource and come up with a plan to incrementally turn it into biochar. It may need to be cut and seasoned for a while first, and you may need to invest in some tools/equipment to do it. However the benefits are manyfold, and will persist in the soil for generations.

if your want agroforestry, whats wrong with working with what you have, are the existing trees marketable, or can you create a market for them?

In the long haul there's no difference how you get rid of the residue of clearing the land. You will get the same change to the environment. You can do it now in the short run or wait for nature to do it for you, I have let the stump of an 18" hardwood sit and decompose. The stump was much bigger than 18". It only took 10 or 12 years and it converted to a powdery mass. It's gone. I mowed around it all those years. So I'd say that if not for the mowing that I'd have the beginnings of a new forest there. So that means that if you don't do something to get rid of the stumps and other residue that you can't use the land....period.

You can get rotary grinders, or riding stump grinders, or you can burn them. If you live in suburbia you might need a burn permit from your voluntary fire dept. If you burn one stump it will take days to burn it. But watch the direction of the wind and the intensity, and don't burn when it's dry. When the wind sturs up the smoke stays low and bothers more neighbors, if you have them.

I googled stump shredder. The first two google returns were for a 500 HP Morbark. It's a video but you get the idea, but with a video I got no idea of a price. Thru google I also saw a 110 HP Vermeer riding stump grinder. From my experience it took days to burn a stump from a 30" Wild Black Cherry.  It took me a couple hours to dig that one stump with a John Deere high lift. I got the bucket under the stump and couldn't lift it. I thought for a while that I'd never get the high lift out from under that dang stump. Then there's dynamite.  Maybe a couple oxen? Take yer pick.

People who build homes and clear land are doing that job for us. We need homes to live in, we need land to grow the food for the billions of people this world supports.

It would be a tremendous loss you may not recover in your lifetime to burn if you have established forest. Tropical nutrient cycling is very rapid. In addition to this, around 30% of the nitrogen in tropical rainforest systems comes from the epiphytes living mostly in the canopy.

Shade is another crucial factor to consider in tropical cultivation.

If it were me I'd spend a year on the property without doing anything except study it and surrounding properties/businesses. Seek out local permies and ecological science.

Rainfall will also be a crucial factor, without trees taking up water and sheltering soils from the weather erosion prone land erodes. With next to no topsoil you may lose the farm before you farm it.

Some selective thinning, and turning those thinnings into biochar might be extremely useful if you are on a clay base. Check out Terra Preta.

F Agricola wrote:Hello Windy,

Really need more information but at face value:

I suggest burning is very detrimental and destructive. Hopefully you're not clearing virgin rainforest?!

It's the sledgehammer approach often used in Third World countries with very dodgy laws and enforcement practices.

Importantly, how would you control a fire and stop it spreading to neighbouring lands? If a fire reaches the canopy, good luck.

Besides releasing huge volumes of greenhouse gases and other pollutants, it wipes out all manner of species that would otherwise be beneficial. The carbon and nutrients created by burning only last a short time - there's a lot of information on the web regarding this e.g. Rainforest clearing for palm plantations, etc

Although a PITA to do, selective clearing is by far more acceptable. That would normally involve a small number of people, chainsaws, and some vehicle/animal capable of dragging logs out.

A description of the property and your intentions would assist in further feedback.

I can't give an exact description, because I haven't started a serious search for property.

Ideally, I want something that looks like this:


Basically something that was clearcut and is naturally in the process of restoring itself, with the brush not much higher than head height or ten feet. At least, in this case I would know that the soil is capable of sustaining a forest, whereas I might not be sure with cow pasture or a completely denuded landscape. Also, the brush would still be a manageable size.

The plan would then be to root rake doze this head high brush in a way that would preserve most of the litter layer, while piling the above-ground vegetation. I want to chip the piles and compost the chips with added manure. I have a custom cover crop mixture planned, which would need to be raked into the litter layer after (or during?) the land-clearing phase.

Kyle Neath wrote:Context matters a lot for these types of questions. Burning around these parts, which is a fire-adapted conifer forest, is extremely beneficial. The ashes help clear out undergrowth (allowing more sun to the soil), clear out pine duff mulch (allowing more seeds to germinate), the ashes sweeten the soil opening up room for succession species (building more soil and root mass), and stratify fire-adapted seeds (resulting in an increase of fire-adapted species). But this entire ecosystem is built on fire.

One of the key differences in fire-adapted temperate climates to wet tropical areas is where the nutrients are store in the soil. Here, they are stored deeper in the soils — in decaying root mass and other forms of life. In the wet tropics, it is often stored in a dense, thin layer sitting right on the surface. Organic matter never gets a chance to be incorporated deep into the soil, it just decays on the surface. That's one of the reasons fires are so destructive in the tropics — that thin top layer of soil is easily destroyed by a low intensity fire.

Thank you for helping me see this. It is true. The soils are very fragile, when exposed they can also be easily eroded by rain and UV light.