Desert Carbon Sink, and other "Greening the Desert" questions

Hi, all!

First of all, don't get me wrong: I'm all for a) working to reverse man-made desertification, and b) planting, tending, and encouraging regionally appropriate plants wherever we find ourselves, to restore balance and healthy carbon and other nutrient cycling.

Gradually growing to love deeply the high desert grasslands where I live, however -- and, frankly, seeing a number of young permaculture enthusiasts arrive here having bought land sight unseen and announcing that they're going to launch grand waterworks bringing water from the mountains to the valleys and "green the desert" and seeming to scoff at everyone around them who's learned to live within existing cycles and work with them to gently redress imbalances -- I've started to wonder: Is there anything inherently wrong with this kind of system, i.e. is it inherently unbalanced? Do we in fact need to green all deserts?

I came across this from our neighbors at the Center for Biological Diversity in 2008: https://www.biologicaldiversity.org/news/center/articles/science-07-13-2008.html. And then this from our neighbors at ASU in 2020: https://www.eurekalert.org/news-releases/839235

I'm trying to learn more about things like the place of mesquite in our high desert grasslands, with the help of a local woman with a degree in rangeland management. We love this tree so deeply, and I hate to hear ranchers call it "invasive" and -- especially -- spray the crap out of it with aerial herbicides (which, frankly, don't have much effect in the long run, as mesquite is as stubborn as we are and comes right the f*** back). But she's starting to teach me some subtleties.

Meanwhile, a clear issue is the rapid depletion of our groundwater, which is an ancient resource that we are using far faster than we can replenish. Many who work to "green the desert" pull up more of this groundwater to establish trees that can't survive here without those wells. When they move on (as we all do eventually, whether we die or our wells run dry because of others' overpumping or etc.), the trees die.

Now, clearly, a few small forest farms are not by a long shot the largest, most problematic water users, and we are working hard to plug those enormous leaks.

But I'm just wondering: Should we really be advocating for any kind of well-fed greening of deserts? It's so rare to hear of folks who are working without wells. But can't we just work gradually and gently with the land to lose less rainwater to evaporation, runoff, and contamination, and work to help it infiltrate while feeding our plants on the way? Can we focus on trees and plants that can survive here on their own, so that our efforts outlast us?

What are others' thoughts on all this? Thank you!

earlier today I posted a link to a video that shows successful forestation of a desert in a thread I started called transferforming desert to forest. ---- yeah with all the new words and acronyms of the internet age thought I'd try my own new words out---I dont believe they even irrigated the trees they just used trees that will grow with very little moisture. there have also been very successful programs in the Mid East and china transforming  desert to forest and then the new forest actually becomes like a whole new aquifer and all types of microbes begin to grow in the newly transformed sandy soil of the new forest floor.

I feel like I see a lot of folks talk about greening the desert in a way that seems, I guess I'd say unrealistic?  Great enthusiasm, but to the point that there seem to be some unrealistic expectations of what can be grown sustainably in the environment.

We can help our deserts become as fruitful as they possibly can. Deserts can be beautiful. There can be some amazing biodiversity. But it's not the same thing as creating, say, a forest the likes of which Tolkien would be proud of. And I hear so many folks talk about the last concept as if that IS what is possible.

I do not believe it is, and have seen nothing yet that contradicts that belief, at least if one very important factor is part of the equation: sustainability.  

I believe the sustainability is an inescapable part of the entire concept of greening the desert, but it gets left out of a lot of discussions about it. Not in regards to sustainability for plant life, for nutrients in the soil, or anything of that nature...but for water.

If we pump out water from the ground, in a desert, to irrigate our plants? That's not sustainable. Yes, gray water helps us use less water, but desert aquifers only have so much water, and with drought (which is happening in my area of the world, for example), water is being pumped out significantly faster than it's refilling the water table.

So when I hear someone talking about using water pumped up from the ground and also using the gray water from it to irrigate anything so that we're using 'so much less water' - which I hear a lot of folks talk about around here - it kind of feels like someone talking about a great deal they found on a new car when they are already in debt and have no money in the bank.

We cannot escape the fact that rainfall as a limiting factor for plant growth in a desert, if we truly want something to be sustainable. Deserts only get 10 inches of rain a year. We can set things up so that there is more shade, there is richer soil, there is more retention of moisture in the soil and as little evaporation as possible...we're still not getting more than 10 inches of rain a year. And that will only sustain a certain number of plants and animals.

And it's not enough to make a huge forest, typically. At least not of the kind I usually hear a lot of new-to-permaculture-and-deserts enthusiasts talk about.

Although sometimes, the problem seems to be a kind of disconnect between the details of various success stories and the reality of the average individual's permaculture project.

The success stories for greening the desert that involve 'lush forests' seem to fall in one of two categories:

1)  Areas that had man-made desertification that was restored successfully BUT that have higher rainfall than a true desert. For example, the Al-Baydha project is in an area that gets an average of 21 inches of rain a year, twice that of the highest desert annual rainfall.

2) Areas that are in true deserts, like Lawton's Jordan project, that got a lot of water from a non-rainfall source to start everything off, and which typically involve plans of extra water sources to be continually added. Sometimes it's added gray water, which is not sustainable.

Or they are in a rare place in the desert where there is an oasis or year round running water, which is very location specific and not a plan many of us can follow.

Or someone is blocking water that is running from a larger source, which is great for them, but screws over every living thing downstream. like the CCC-built swales in Tucson, AZ.

I'm not denying that these success stories have some amazing growth. They do. But so far, I haven't seen any that didn't involve rainfall PLUS extra water to achieve it. If anyone has some that they've found, I would honestly love to see it, truly, but I haven't found any myself.

So nothing we do is going to change the fact that there is not enough water to support more than a certain level of vegetation, period, end of story. Brad Lancaster's books on water harvesting have a great chart in them about the water needs of various trees and shrubs, and I think it is worth a read for anyone wanting to green the desert because you find out really quickly that your land is only going to support X amount of vegetation.

If a desert is only appealing to someone because they plan to make it as green as Ireland, they're likely going to be disappointed, I think. If they are just looking to put in a lot of desert vegetation that is in the best possible situation so they have more growth than the typical area around them? They're likely to be happier.

Now, philosophically, the question of 'should' we green all the desert we find? I don't think we should. There is a lot of biodiversity that exists because of deserts and would die if we actually succeeded. Not to mention that there is an ecological purpose for deserts, just like everything else. For example, deserts are a net carbon sink. Current research is suggesting that bacteria located in aquifers beneath sand and in the sands itself in at least some deserts are capturing carbon from the air. (https://www.sciencedaily.com/releases/2008/04/080401200451.htm).

I do think that we can still help deserts become the best they can be, in a lot of areas, but I think deserts BEING deserts is still a good thing, too. I'm admittedly a little biased - I grew up in one desert, moved to a more temperate area and a coastal one, and ended up back a desert because I love being IN a desert, harsh as it is.

And I also am a huge fan of the whole concept of 'planting a tree that your grandchild will be able to sit under.'

Of course, I say all this and my land? It's not sustainable right now. I have some plants I have to irrigate. I am still working on water harvesting. I don't have things all completed or even all figured out on my land. I'm just very aware that some of my plants aren't sustainable in the long term, water-wise, is all.

Thanks for asking these questions. These are things I've been thinking a lot about too.

EDIT: LOL. I read your question and didn't get to answer it until much later, and totally forgot you had already mentioned the whole carbon sink thing, ha. Great minds think alike, I guess. ^_^

I think the only truly viable way to "green" deserts is through water harvesting earthworks. Definitely not bringing water from the mountains.  And I personally believe the only deserts that need greening are those damaged by human activity. I believe our responsibility as permaculturists is to fix our own messes, not go looking for existing natural landscapes to "improve".  There is plenty of obviously damaged land to repair, including dry climates if people prefer them. I think natural deserts will do best being left alone, in most cases.

Driving through the southwest one can see huge areas of land devastated by past farming (cotton, I think). Best to work there,  I think,not in the lovely natural desert landscapes where, unfortunately, a lot of people want to go live.  

Moving to marginal landscapes which are becoming desertified through bad management, and repairing them, is a good strategy, I think.  That's what I'm working on at my own place, a small patch of ranchland severely damaged by overgrazing in the past.  Just a limited amount of earthworks have done tremendous good.

Hi, sorry for not reading all the answers.

I think you could remember the zones in Permaculture. The last zone (zone 5?) was meant for wilderness. That should say everything.
In our project, we have left a 10% of the space for wilderness, even if it is not really zone 5.

I think the problem is that the dumbed-down version of anything doesn't necessarily work. So if someone hears "hey, it's possible to green the desert" and goes about it the Disneyland way, or the way they build golf courses in Phoenix, then they haven't done any good, to say the least. Running the Colorado River dry and pumping out the aquifers are both ecological disasters.

I'm with Ludie on the value of water-harvesting earthworks. It's vital, especially in a desert where rain is infrequent and torrential, to slow water down and allow it to soak in. Geoff Lawton in his PDCs goes into a great amount of detail about these earthworks, and on strategies to recharge desert aquifers. He certainly advises against well-pumping aquifers in desert climates for many reasons, one being that salt water normally flows in to replace fresh water pumped out, and keeping the salt water table low is vital in a desert to keep any potentially productive land from salting up.

Another rule of thumb he used to talk about is that cultivation may be possible in deserts in a ratio of about 1:20, meaning you might need 20 ha of well set-up land to make it possible to cultivate 1 ha. And in many situations, a savannah-like environment can eventually be created, but no, no Amazon rainforest. In any case, the interventions that are possible can tremendously improve the water cycle. I think the idea is to turn barren desert into a place where some cultivation is possible in certain well-placed pockets around the landscape, and the water cycle can be improved all around.

Trees to be established need some water from one source or another. If you know what you're doing, it can be well worth this water to "prime the pump" and establish some trees. Trees are vital to restoring the water cycle, decreasing temperature, increasing humidity, seeding a bit of convective rain in places, and allowing more life to establish itself around them.

The figures mentioned for rainfall in Saudi Arabia (Al Baydha project, ~50km south of Makkah) threw me for a little bit of a loop, I think there must  be some confusion between metric and imperial measurements or something. After a lot of research, I think I can confidently say that no place in SA gets 21 inches of rain in a year. In a paper I downloaded here, p.24 lists all the weather stations in SA with their average rainfall. The highest is Abha, far to the SE of the Al Baydha site, and up in the mountains at 2100 m altitude, and even so the average annual rainfall is 230 mm or 9 inches of rainfall.

In this permies thread https://permies.com/t/40248/months-growth-swales-Saudi-Arabia, Neal Spackman who designed the project stated they get about 70 mm a year (under 3 inches) in the area, and that in the last 5 years working there, it had rained twice. So I'd say it definitely qualifies as desert. If you watch any of the videos, you can see that the earthworks improved the situation, even if most of the trees later died once drip irrigation was removed, which I understand they did. However, the trees that survived are now known to be adapted to that climate, which is really something IMHO.

As far as Geoff's current project in Jordan (his first "Greening the Desert" project there was abandoned after some kind of problems with property owners or project sponsors I believe), I think it's also a tremendous success, even if on a small scale. It's quite urban, in a West-facing village (think intense afternoon sun in the desert heat) located below sea level in the Dead Sea Valley. They certainly do all the rain harvesting possible on their small site, and yes, they do use all their greywater in the gardens, as well they should, and if they managed add more to it from the rest of the village, I think that would be great too. In those areas, you can't let greywater go to waste, so well done.

Another question is where did the fresh water that people in the village use come from in the first place, and is that sustainable, a question I don't know the answer to. But in any case, if people are taking showers in the village, of course the smart thing to do would be to use the waste water productively rather than throwing it away. Maybe, I don't know, there's more to be done there in terms of sourcing fresh water sustainably for the villagers in the first place, but for now, starting from the real situation on the ground, I think it's a great victory that in a dusty, parched, poor village totally dependent on imports he's got people producing loads of their own food for the first time, optimistic and sitting under the shade of trees they've planted themselves.

I'm interested in the idea that the CCC projects in Arizona had any deleterious effects, have you got any more info? I can't imagine how swales and check dams, allowing the water to slow down and soak in, and even allow some streams to run much of the year where they hadn't before, could be anything but beneficial for those downstream. Do I just have my rose-colored glasses on? Honestly interested in hearing more about this.

And lastly yes, let natural desert stay desert, while working to repair the huge ecological damage previous and present generations of our species have done, and allow nature to regenerate the Earth's natural diversity and abundance.

Anyway, in sum, I think greening the desert has it's place, and well thought-out permaculture projects in the desert can have a great impact on people and the Earth. And of course, anyone who just sinks a well and pumps out the groundwater to green the desert by adding an English lawn, is a nutjob. IMHO. You gotta know where you are, and what you're doing.

Dave, I think the concern comes when the extra humidity modifies what species can grow there. Think of a desert so arid that only cactus can grow. Now you change the terrain, allow for more water infiltration and then you have some extra trees where you had none before. The new vegetation is home to new creatures not present before. These creatures might be a threat for the old species that were adapted to the extreme climate, and might even substitute them in the ecosystem.

You could think that the extra moisture would just increase the amount of the previous species, and this could be what happens at the beginning: you could have just more cacti. But desert plants grow very slowly for a reason, that's their way to stay alive in the environment. When a plant with higher water requirements is introduced, this plant is going to grow much faster and will not die since you have artificially increased the amount of water absorbed in the soil. Well, the new plant is going to outcompete the old ones because it grows faster, so it can win the battle for the resources.
When you change the conditions, the ecological niche is going to be filled by species best adapted for the new conditions sooner or later.

You might prefer trees to cacti, though. Arid deserts are not very useful to us, but they are useful to many wild species that can only thrive if their environment is kept as it is. That's why zone 5 must be left as wilderness: to preserve the ecosystem base.

Some random thoughts to interject here:

Greening the Desert has some advantages over other places.

Giving enough water, you can grow year round (well almost).
In most of the fall, winter, some of spring .... evaporation rates can be controlled pretty well through mulch, smart watering, etc.
Especially if you want to grow something fast, and have the water and resources to do so.
Many of the trees in the desert are ferocious growers.

Another thing to think about, from a carbon sequestration point of view .... in dry hot deserts, wood/and organic matter, doesn't breakdown and re-atomize into airborne carbon much.... not anywhere nearly as fast as say a traditional 'wet' forest.   Sucks from a soil building point of view; but not from a carbon sequestration point of view.

Dave de Basque wrote:
The figures mentioned for rainfall in Saudi Arabia (Al Baydha project, ~50km south of Makkah) threw me for a little bit of a loop, I think there must  be some confusion between metric and imperial measurements or something.

You are absolutely right - I screwed up. Don't know how, but accidentally mixed up my figures for the Asir Mountains with the Hijaz mountains. *head desk*  You know, only picking the highest rainfall in all of Saudi Arabia to mess up with, LOL. Thank you for catching that!  I'm curious to go explore it more.

Dave de Basque wrote:
I'm interested in the idea that the CCC projects in Arizona had any deleterious effects, have you got any more info? I can't imagine how swales and check dams, allowing the water to slow down and soak in, and even allow some streams to run much of the year where they hadn't before, could be anything but beneficial for those downstream. Do I just have my rose-colored glasses on? Honestly interested in hearing more about this.

re: the ccc projects...maybe a little rose colored glasses? This one is near and dear to my heart, because this is in the part of the world where I live now, and close to where I grew up as well, so I feel more informed about it.

I guess the first thing would be briefly discuss what kind of waterways we have here.

Aside from a few rare areas, the majority of this desert (including where the CCC made their swales) contains ephemeral streams (or arroyos). These are only fed by rain fall, as opposed to underground water sources, and water runs in them for mere hours to a few days after a precipitation event. The vast majority of these rain events happen during a 2-3 month period.

So the majority of this area has no running water during the year aside from rainfall (the only one we used to have was just one year round river, from an underground springs source, and a business group, early on when Europeans came to the area, sunk in wells at the source and the river ran dry in just a few years as a result).

So there really aren't any streams that would run more of the year...heck, our ephemeral streams running even a full week, let alone a month, seems very unlikely.  It's just not how this environment works, even without any human interference.

Now, can I say that I've seen the evidence first hand of the damage from the CCC swales? Yes and no.
I have seen no research on it, or any of the other CCC projects in this area. Not really an area the government much cares about right now, ya know?

But I can speculate on what I see elsewhere in this same environment, and even what I've seen in that area (it's a place I can drive to and hike around fairly easily).   And from what I've seen, the swales like the CCC one cause problems because of the size of our rain events, and the frequency.

Something that slows down the water a LITTLE is not bad. We have periods of erosion and alluviation in our arroyo systems, but these are sometimes problematic with human habitation and avoiding damage, so yeah, we've got to do something to help slow down erosion, if nothing else.  Give the water a teeny bit more time to soak in just a little here and there can help with that, help a certain area. Get a few more plants in the area, a few more animals there.

But while we get a couple months with some LARGE rain events, the rest of the year, it's not uncommon to only have small rain events, and the plants and animals need to get every last ounce of that water to help them survive.  Water from just one missed rain event can mean the difference between life and death, at the wrong time of year.

These non-monsoon rain events are often small enough that even a moderate swale and check dam don't slow down the water, they just stop it completely (placement and size matter, obviously). And because the next rain event may not be for weeks, or even months, a lot of the plants and animals downstream can't survive the loss in expected water, so it lowers the biodiversity downstream, even if you get an uptick in plant and animal life at the swales/catch dams.

We even run into this with mulch - many rain events here aren't heavy enough to fully soak into the mulch, so inches-deep mulch with no irrigation can result in the mulch getting a bit of rain, absorbing it, and releasing it back into the air without the plant even getting any water.

So in areas where I have seen the water blocked by something that was too large for the water to fill and flow over during average rain events (which the CCC swales most definitely are), it does more harm than good for life trying to survive downstream from it. At least in my experience.

Hope that makes sense...bit sleep deprived today, so I'll have to go over this later and make sure I'm coherent.