Leaf Litter

Leaf Litter Talks with Jim Harris

We hear from Jim Harris, a Professor of Environmental Technology at Cranfield University, about his love for soil.

By Amy Nelson

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How did you get interested in soil?

It’s funny, really. I had very little interest in soil until I went to college. My first degree was in applied biology, and if I was to be given a subject discipline, it’d be a plant biochemist. We had some soil lectures during the course of that. I was about to go off and do a Ph.D. in seed germination, and the role of light and dormancy breaking. I had some theories about the biochemistry of that that I wanted to test. …and money was pulled by the Thatcher government across the U.K. and my supervisor had some money available to look at, of all things, aquaria filter materials. It was substance called zeolite. Essentially what happened was these materials absorbed lots of ammonium from the fish and the bugs start to work on the ammonia and convert it to harmless compounds, (which means you can get your fish into your tank much sooner than if you use traditional filter material) and I got to think about, well, okay, now I’ve got this fish tank…what can we use this material with when it’s finished? I thought about my soil lectures and some of the things we heard about deep mines and I wondered if places like British Coal would be interested in using this material to improve the nutrient retaining capabilities of coal soil from deep mines. It’s a long story, but essentially I organized a meeting with the wrong research director. I gave him some schpeel about this and his interest was not deep mines, but open-cast (strip) mines. He said, “this stuff’s too expensive” but if you want to do a Ph.D. in soil storage, I’ve got the money.” So I became a soil microbiologist…self –taught. I did a Ph.D. on the microbiology of topsoil storage, which, although it’s over fifteen years old, it’s still quoted left, right and center. It all took off from there. I became utterly fascinated with life in the soil and with the concept of putting ecosystems back together.

What do you think poses the greatest threat to the quality of soil?

Most of the pressure comes from population size on the planet and lack of wise use of resources. Looking at the list that you’ve given in the survey of your readers, there are two of particular high impact. Modern agriculture – methods involving extensive cultivation of soils. The other is global warming. Global warming is having a huge impact. This is a hot piece of news. There is a paper coming out of Nature which has come out of people working in this department who have looked at soils in England and Wales over the last 25 years. Over that period of time, irrespective of land use, something like .06% soil carbon per annum is being lost from soils. That’s a huge amount. That means, in certain circumstances, 50% loss of soil organic matter over the last 25 years. The only thing which seems likely to be a candidate that could explain that, would be global climate change. So soils have gone from being a net sink to a net source of carbon. That will then have all sorts of effects in terms of erodibility, nutrient relations and things like that.

Very few Leaf Litter readers cited global warming as a major threat to soil in our survey. Why do you think this is?

Very often, ecological practitioners are rooted in the local for all sorts of reasons. They kind of think of global events as “oh, that’s important, but does it really matter to me” or “what can I do about it?” As many people pointed out in your survey, there’s an ignorance of the fact that soils are living, dynamic systems. You raise the temperature, and living systems start working faster. People don’t necessarily make that connection.

Our readers seem to think that the greatest misconception about soil among the general public is that “dirt is dirt” and it is replaceable? Would you agree?

That’s definitely the case, and it’s a huge problem. It’s coming back to the fact that people just see soil as “dirt.” We hear the terms of “dirt farmers” and “things are dirty.” When you talk to gardeners, they’ll talk about “soil and earth.” They see soil as synonymous with earth, so that it’s valued in that sense. Gardeners certainly tend to take great care with their soils and have a great bit of interest. Farmers are, but more in sort of “what can I get out of it.” Consequently, if society as a whole doesn’t value soil as a living and irreplaceable resource — certainly irreplaceable in the sort of time scales we’re interested in — there’s a lot of trouble ahead.

When we asked our readers about research they’d like to see, so many asked for case studies to help address the problem of public education. Are there any resources that you know of that are documenting case studies in soil restoration?

There’s lots in the scientific literature about soils and restoration. There’s a big subsection where soil resources are directly addressed. There’s a greater body where soils are included as part of a number of measurements that are taken. There’s not a tremendous amount that’s out there in terms of what practitioners might be interested in, in terms of restoration, and perhaps it’s something we need to address.

On a scale of 1-10 (with 10 meaning most critical”), how do you think most people involved in ecological restoration would rate soil in terms of its importance to an ecological restoration project? (Most of our readers gave it an 8, 9 or 10. Does this seem believable?)

When I see practitioners who are cognizant of ecological restoration, then I can believe this. There might be a sort of self-selection in the survey because people who are into ecological restoration will understand the fundamental importance of soil as a starting point for anything. If you’re talking about a wider community than reclamationists, then soil will be seen as an important part, but they might regard civil engineering aspects as being more important. Certainly the tension between civil engineers and ecologists has always been one of the reasons why many restorations don’t perform in a way that would be hopeful.

Tell us about your current research

I get involved in a number of levels. One of the main things I do is development of soil microbiology called methodology for looking at the size, composition and activity of the soil microbial community. How those methods can be deployed to assess the quality of ecosystems and the success or otherwise of programs designed to reinstate functioning ecosystems. The fundamental spinoff is looking at function and biodiversity relationships. What is the relationship between biodiversity and functionality of systems? Functional redundancy. I also spend quite a lot of time thinking about and writing on the development of conceptual frameworks within which ecological restoration is set. The restoration ecology angle. That’s when I work with people like Richard Hobbs and Rudy van Diggelen on ways in which we can think about what we’re doing, how we set targets, how we measure success, and principally, what is it that we’re after. This is where many of the conflicts and misapprehensions occur. In terms of what’s available for practitioners, my research certainly provides tools for assessment and to a large extent, I would hope, setting of context in which they’re working and setting goals and aspirations for what they’re doing.

What type of soil research do you think is still needed to support the practice of ecological restoration?

There is a lot of work to be done on assessing and developing means of manipulating microbial communities. Particularly with respect to the way in which microbial communities permit or prevent establishment of desirable plant communities and then how that fits in with how the whole ecosystem works. Most people involved in ecological restoration know of the importance of fungal symbiosis of plants, but there’s a much bigger story out there. For example, quite a lot of work has been done over the last decade on the importance of microbial communities in facilitating invasive species establishment. If you take a species rich grassland, in a way it’s quite fragile in that all of those species will have their own set of pathogens that they’re constantly battling with. It’s thought that it’s that load of pathogens that keeps those systems diverse, because every one has got its own pathogen. So it helps in the competition between plants, and nothing becomes dominant. When an invasive plant turns up which has no pathogens, it runs amok. So simply putting down a soil system and expecting to establish a species-rich system is not going to work unless you consider the microbial community. We’re a long way from being able to manipulate the microbial community in that context.

The other thing that we’ve got to do, in particular the light of the work that’s come out this week [on global warming] the importance of using ecological restoration as a means of tackling CO2. What are the strategies that we can employ to actually use new ecosystems to sequester carbon. What sort of systems will start burying carbon for us? That’s going to be critical. There’s a lot of work to be done there.

What can we in the U.S. learn from some of the work you see and are involved with in other countries?

The Russians have got this amazing term called the “technogenic landscape.” In Europe, it’s very difficult to find areas that you in the U.S. would recognize as wilderness. We do have some big areas in places like Poland, but they are few and far between. It’s very difficult to find untrampled upon areas, but there’s lots of work done on large-scale disturbance and fantastic work done on strip mine restoration. For example, Karel Parch, who has done a lot of work on natural recolonization of strip mines, and Jan Frouz, a soil scientist with a big interest in interaction between microorganisms and miso fauna. These are just examples. There is all sorts of stuff going on all over the place. There’s work going on in the Netherlands with wetland restoration. They’ve got some very sophisticated models of exactly what you need to do in terms of soil conditions, hydrology and maps of sources of propagules and what’s likely to establish. There’s a lot of predictive work there. That could be usefully employed in the States. I’m absolutely sure about it. There’s all this strip mine stuff. There’s lots of stuff on the interaction of establishing functioning ecosystems within areas of development and areas which have been developed and need to have ecosystem services reinstated. I think there’s a big crunch coming for us with global climate change, where we really have to examine where is it we need to be and what should be the object of our interest. I’m fairly well convinced that the object of restoration should be ecosystem services rather than particular species assemblages, because the situation is changing so quickly. Putting down a woodland of a particular sort that would have been here historically 50, 500, or 1000 years ago that’s going to take 300 years to develop, well in 300 years’ time, the biogeoclimatic conditions will be so different that that woodland will not sustain itself and we need to think about flexibility. You get lists of species that you want to see on a site, but you have to think very hard about the role, for example, of exotics in establishing ecosystem services. That’s a really tough one for some people, because they like to think we can put this back the way it was so long ago. You can go to points in Europe, where if you dig a deep enough core out of the ground, you can find a shift on a particular site between eight different ecosystem types, vegetation types, in the last 1000 years. This concept of target, and being focused on one particular species, is a really tough one.

Do you believe Europe is ahead of the curve in terms of factoring in global warming?

The recognition that global climate change is happening and is being caused by humans is an absolute no-brainer in Europe. Everyone accepts that. It’s very unusual to find people who don’t accept that it’s happening. The evidence is piling in day in and day out. The fact that we need to be doing something to mitigate that is really coming to the fore. How exactly we’re going to go about that is still being formed up. Although there might be a rush to renewables as a potential solution, in the medium term that’s not necessarily going to be a solution. We really need to think about the allocation and management of land resources, and I think that’s where ecological restoration can have a big impact. It’s funny, because in many senses, the U.S. has been practicing that sort of thing, in terms of large areas of restoration, but in Europe, it has sort of been built into what a lot of the conservation bodies are doing anyway.

What do you think about theories suggesting that most earthworms in the U.S. are invasive, changing soil chemistry and facilitating “takeovers” by exotic plants?

This question intrigues me. I think there’s quite a bit of truth in that. But the question is…would these earthworms have turned up eventually anyway because of the retreat of the glaciers? It may be that we’ve simply accelerated something that was going to happen anyway. I don’t doubt, looking at the bits of evidence I’ve looked at over the last 24 hours, that they will have an impact on soil chemistry. Traditionally in Europe, they’re regarded as a good thing, an indicator of healthy soil, because they do stabilize soil structures and they will stabilize soils in areas that are otherwise eroded. One of the big problems we have in parts of the UK, is an invasive New Zealand flatworm, which actually predates earthworms and has led to decreases in aggregate stability and increases in erodibililty. It’s interesting the way one person’s meat is another’s poison. I think there’s an area here absolutely redolent with possibilities for further research work, particularly as it pertains to impact of earthworms on carbon storage and stability of carbon compounds in soil. That, of course, plays in the climate change arena also. I think it’s fascinating. The question is, can you do anything about it? The answer: probably no, because they do get about.

Your work seems to be focused primarily on the biological properties of soil. What advice or sources of information can you recommend on the subject of restoring the physical and chemical properties of soil?

Apart from the excellent textbook by Harris, there are all sorts of bits and pieces out there. You do have to troll a bit through the primary and grey literature.

Do you have any “fun facts” about soil you can share with us?

If you looked in a species rich grassland and you had a hectare (about 2.5 acres) of soil, if you could imagine all of the microbial biomass bubbling up through the soil and coming to the surface in the shape of sheep, you’d probably have about 500-1000 sheep standing in your field. It’s a huge biomass.

The largest organism on the planet is, in fact, a fungus. This fungus covers several hundred hectares. It’s all one individual, several thousand times larger than the blue whale.

Any simple things you can suggest that our readers do in their own backyards to restore soil?

Stop digging it over! That would be primary. Put compost on the top. That’s absolutely fine. Stop spraying it with chemicals.

Do you have any thoughts about the role of soil in the flooding of New Orleans?

There’s a huge story there about the restoration of the wetlands south of New Orleans. I think that proper attention to restoring those – it would have to be a huge program – would make a significant impact on protecting it from extreme weather events. As I understand it, huge areas of wetlands are lost there daily. I heard someone on CNN Saying they estimate the losses of two football pitches per day of wetland. That really is mad. That needs to be halted and reversed. You see, we get these ecosystem services and regulation from functioning ecosystems, and if we ignore them and believe we can do it all with hard engineering. We’re going to come a cropper.

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