Professor David Thomas is a renowned drylands scientist with a background in geomorphology and extensive field experience in arid and semi-arid regions. He has authored over 80 peer-reviewed articles and many books on drylands. Much of his current research work is in collaboration with social scientists, to understand how we interact with our environment. In this interview, Professor Thomas shares his experience in the remote Kalahari Desert, offering unique, ground-truth insights into the much-needed solutions for land degradation.

You’ve been working in dryland environments for 35 years, largely in Africa. What would you say are the biggest changes you’ve seen over that period?

I’d say the two primary things are the expansion of bush encroachment, which is a big, interesting issue in many global semi-arid regions, and, the other is the increase of reliance on groundwater as a means to support agriculture and even pastoralism. The latter is pronounced in environments with uncertain precipitation. I also think it’s partially being pushed by the desire to have production in areas otherwise unsuited to it. I’ve done a lot of my work in the Kalahari. That has been transformed by very simple extraction of groundwater at a large spatial scale, which has meant that environments that people only dipped into in years of good rain are now available 24/7 for pastoralism.


So this push for productivity has really affected the water table, then?

Yes, it has. It’s really hard to calculate it. There was an attempt some years ago to try and calculate recharge rates in the Kalahari, and they are way below extraction rates. Of course, this is the same elsewhere. In the US, with the Ogallala Aquifer, for example, you can see two things happening: the water table dropping, and the water quality diminishing.


Do you think these problems with unsustainably demanding more of land is on the rise, or is it more of a steady change in land use?

I think it’s happened for different reasons in different places, and at different scales. In the Kalahari, it kicked off post-independence, and was part of a great attempt to free up the use of resources and increase productivity. There was a strong cultural element in Botswana, because people love cattle, and it meant that people could graze cattle all year round, in places that had only been used seasonally. As a very old friend of mine who still lives and works out there always describes it, it’s cattle mining. It has big implications on an environmental system that is not naturally used to grazing pressure all year round, and it’s unsustainable in the medium to long term. In the case of the US, it’s linked to issues of food security and satisfying the insatiable demand for products to feed livestock, rather than cereal to be directly consumed by people, which in terms of energy, and environmentally, is far more efficient.


In the areas where you work in Botswana, would you say these land-use changes are driven by policy?

Yes, it was enhanced and enforced by policy changes. Really, what gave it weight was European subsidies to the Botswanan beef market. Under the Lomé Convention, Europe paid above market rate for beef as a development tool, so it encouraged people to have more cows in places where they weren’t previously. In other places, it’s been bizarre the way countries that don’t need to produce food, like Saudi Arabia, have been keen to test out their potential to tap groundwater and grow crops. You have scenes of center-pivot irrigation in the middle of areas with very large sand dunes. It is very unsustainable, and salinization soon results. I think, given that water is a driver, above all, in drylands, if you have access to water year round, then at the local, national, and even international scale it’s seen as a panacea to increase productivity.


So ultimately, what are the biggest challenges for future land use, not just in Botswana, but in all dryland regions?

Professor David Thomas drills in Sua Pan, Kalahari, for cores to analyze long-term climate and vegetation change data.

Well, my views have changed dramatically over 35 years. I would have said back then that the biggest challenge is land degradation. But, the challenges of growing populations, and the need to feed people make things very different. So, if I were to name two, first I would say urbanization. We can look at the developed world too in this regard: look at the environmental folly of Las Vegas, for example. But, there are equally significant, even larger scale, issues in the developing world from the huge increase of urbanization. This has the dual impact of more people who aren’t producing food, but need feeding, and less labor available in rural areas.

However, I think the biggest challenge of all has to be global warming and its impacts.  Particularly in dryland regions, this is one of the biggest uncertainties that prevails. The scale of uncertainty and the unpredictability of the climate system in low-latitude contexts creates an extra burden—it’s really hard to forecast and plan for the future when these are some of the most difficult areas to model future climate changes in.


Are there any easy solutions or quick fixes to implement sustainable land management?

I think looking for quick fixes is the wrong way around. You have to look mid-term, because quick fixes in uncertain and volatile climactic contexts can easily be quick disasters as well. It’s all about increasing resilience, and not just of the land, but of the people, as that, in turn, has positive impacts on land. Some of the work I’ve been interested and involved in is looking at how people are diversifying livelihoods, as this creates a big buffer against shocks. A positive effect of urbanization is the fact that people are generating income and sending remittances back home. For me, we need to think outside the box for fixes, which really involves looking at the bigger livelihood resilience issue, rather than land degradation in an isolated way.


So what have you seen work, in helping communities and areas become resilient against land degradation and livelihood loss?

We’ve found that a common component to being successful is diversification—not putting all your eggs in one basket. Microcredit has really helped people set up, and think, and actually move in an informed way to improve their agriculture, by taking out loans for fertilizer, buying better seeds, and so on. Those ways all put less pressure on land, so it can be a win-win for people and the environment. A lot of the solutions to pressure on the land aren’t, per se, to do with the land, but to do with the larger economic and social contexts that people live and exist in. The final bit is the notion of education, not just to improve basic skills, but allowing people to learn from others with similar experiences.

Linked to the latter is the expansion of interest in traditional practices and local knowledge. There’s been some wonderful work by people like Mark Reed at Newcastle University, looking at how traditional practices are in tune with the environment, including ways of reading the environment, using the land, and recognizing risk. I think local, rather than global, is often good, but you have to have the opportunity to empower people to use what they know. When desertification and land degradation came to the fore of global issues in the 70s and 80s, I think it was being looked at, at the wrong scale. It was coming out of a colonial era where people hadn’t been able to do what they had traditionally done, or constraints were being put on them, sometimes by new political regimes or even through development. So, giving people opportunities, encouraging and assisting them to have empowerment of activity and more control over their own destinies, can only be good.


If you were to wake up tomorrow in a new world, what would your dream scenario for a stable Kalahari landscape look like?

Access to water remains a major issue in African drylands, even here in the Kalahari’s wettest part, in western Zambia.

Well, you’ve touched upon one of the big dilemmas, because the landscape is not naturally stable. That’s where a lot of land degradation problems come into drylands—this assumption that we’re in a climax ecosystem world where there’s a default perfect case. In reality, the key dynamic is variability. So, we don’t want to enforce a single state, but recognise that the natural state varies. In the Kalahari, one of the big problems over large tracts has become bush encroachment—it’s seen as a terrible thing. But, in some conversations we’ve had with local farmers, they saw some benefits of it: shrubs provide fodder in the dry season, and can actually be a real buffer before grass reappears at the beginning of the west season. Some form of enforced stability has come about because of the impacts of bush encroachment and groundwater extraction. But, stability isn’t the right context for me, and I don’t have an ideal scenario.

If I was a dreamer, I would take down the fences, remove the cattle, stop the groundwater being pumped and allow natural systems, with their migratory wildlife herds, to recover. But, that will, of course, not happen, so we have to deal with a situation of increased human engagement with areas that were once less ‘used’. So, what I do have is a concern of the risk of imposing a rigid solution, especially with the impacts of global warming, on these notoriously difficult-to-pinpoint systems. An ‘ideal’ scenario might be palatable now, but could turn around and bite us in ten years if climate system dynamics lead to, say, a different precipitation regime than was anticipated.


You’ve mentioned the idea of resilience and diversification in terms of income and economics. The Economics of Land Degradation Initiative works with the idea of total economic value of ecosystem services to ascertain more understanding of the value of land. Do you think calculating this value proves useful?

It’s an attractive way of looking at things, but the risk attached to it in a rural, developing-world context is that it gives emphasis to putting people in the hands of those who are making the policies. You’re attaching a value to things in a volatile system that may have a different value later on. It’s also really important to understand what economics means at the local scale. I’m an advocate of valuing local knowledge and information, so I think there needs to be a lot of care attached to that, as to whose economics is being used to attach values to things. A lot of dryland systems and rural economies are not part of the global economic system. They operate at a much more local scale, and there’s a danger that as this scales up to being valued at a national scale, it loses definition at the local scale. One thing I have learned in my 35 years in drylands, is that difference and variability are the only two words you can use to characterise dryland environmental and social systems. They are not temporally stable, and they are not spatially consistent, and I think that’s a real challenge from an economic model.


It’s a complex task, going between all the scales and trying to find a common language between them. How do you feel about the future?

The more hands to the pump the better it is, because that’s where the controversies and differences arise. If I look back at early concerns about land degradation, there were too many singular voices shouting loudly about the right way to do things and what the problem is. I think the big thing we have learned in 35 years is that difference, and appreciating differences, is key to finding the right solutions.


Naomi Stewart

Naomi is currently completing her M.Sc. in Science Communication at Imperial College. Formerly a Project Associate at the United Nations University - Institute for Water, Environment and Health, in the...

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