WRB global reference system with possibility of correlation with national systems (submitted by John Hollis, Allan Lilly and Bob Jones, UK)

[StephanMantelISRIC]

One of us, John Hollis, was involved in the development of WRB during the late 1980’s and early 1990’s. During this time, one of the main objectives was to provide a system, based on the FAO classification, that could provide a global reference system through which the many ‘national’ classification systems used to support soil mapping, could be correlated. The simple two level system that was instigated by Otto Spaargaren was perfect for this purpose, having a top level that encompassed the main soil types present at the global level (according to our current thinking) and a multiple set of qualifying terms that could be used to add detail with respect to differentiating specific pedological characteristics of local importance. This development allowed for flexibility in correlating soil types at the global level, whilst recognising the various regional characteristics that influenced the development of specific national classification systems. It seems to us that, with the introduction of the new annexes and a number of very minor modifications of existing criteria, this flexibility is being increasingly lost.
We would emphasise that this is not a criticism of WRB. It is a very useful system for correlating soil types recognised across the world. Our concern is that it is now reaching a stage where its original purpose is being degraded by seemingly unnecessary minor modifications or additional material.

(submitted by John Hollis, Allan Lilly and Bob Jones, UK)

[StephanMantelISRIC]

Response by Cezary Kabala:
As you know, the most important platform for discussion on WRB is the every-year field workshops arranged by the WRB Working Group (this year in Catalunia, soon in September). Around 40-50 people from various countries spend a week discussing the issues of soil development and transformation in environmental and anthropogenic contexts and testify the WRB rules and detailed solutions (criteria). Moreover, members of the Working Group try to testify and discuss WRB at each other occasion – during the national or international conferences, workshops, and courses. And finally, we use WRB just for teaching, naming, and mapping soils. The results of the latter are commonly published in journals and reports. As you may expect, these are plenty of remarks and suggestions.
Of course, people say that WRB must be continuously developed in line with new soil findings and the development of new concepts, previously unknown, thus not reflected in the classification system. In general, people agree with this statement. But if we start a discussion on particular solutions, we may discover huge differences in the expectations. The best example are Technosols. It is clear that these soils existed always (at least since the beginning of modern soil science history) and people agreed to introduce respective units. But you know how long it took to introduce Technosols as a reference group and how many people were opposed to this. Many national classifications still ignore these soils. Soil Taxonomy probably will introduce a similar order, but many ‘conservative’ soil scientists in the USA do not agree with this ‘unnecessary’ revolution. We always discuss how people will welcome a new unit (at any level) and introduce it when the requests and argumentation are very strong. Typically, proposals for new diagnostic horizons or materials have been discussed for many years. This was the case of finally introduced pretic, murshic, and mulmic. Whereas, the international importance of brunic, a sandy ‘brother’ of the cambic horizon, recognised in some national classifications for many years, is still questioned. In general, most of the proposals are derived from existing national classifications.

[StephanMantelISRIC]

Response by Cezary Kabala:
So, we develop the WRB, because of general expectation, new finding and concepts, and strong pressure to involve some national/local solutions, which may have regional/global importance. It is always connected with the basic question you asked: What is WRB? A general platform for correlation only or the comprehensive international system for soil classification? I feel that supporters of the first option are now in a decreasing minority. With the introduction of Technosols, WRB started a transformation towards the second option.
The development by adding new solutions always results in a growing complication of the system. This is the source of discussion and friction in the Working Group. People consider some solutions to be absolutely necessary and ignore the others. But other people have exactly the opposite opinion. Who is right? Finally, each new solution in the WRB is the result of compromise. You may say that compromise is good in politics, not in science, but the coordination of the global soil classification already is a politics…
When changing the criteria/definitions or introducing new units, we follow proposals of their authors. We try to check/test it, but sometimes the problems are discovered after some time. The best examples are criteria for pretic and chernic in 2014/2015. As early as in 2017 we were sure, the criteria lead to an overestimation of Pretic Technosols and underestimation of Chernozems (while overestimation of Kastanozems). But in both cases, the criteria were constructed based on the proposals of highly experienced and famous professors, supported by many other renowned soil scientists… We really tried to simplify some solutions, but the request of some people and societies to introduce the ‘consequent’ or ‘systematic’ solutions always resulted in their complication (the best case: epic, endic, dorsic). And one more: traditions. This is the crucial problem when we try to change methods/criteria for base saturation and respective horizons/properties. We know the problem you highlighted (‘Eutric Umbric’) and we must find solution for it, but it requires more data and global analysis (eg, if we want to replace complicated and expensive base saturation with simple/cheap pH).
This is why the newly introduced concepts must be extensively tested and may be removed or modified in the next edition of WRB. Thus, your findings and suggestions are important and will be considered - but not now. The next edition is not planned earlier as in 2030. I am sure that the ‘overcomplication’ at various levels (criteria, qualifiers, rules) will be one of the most common topics discussed in the future. If the pressure from the societies for simplification will be strong, we will remove some solutions and will be more assertive in case of new demands... But we cannot stop a development at all.

[StephanMantelISRIC]

Response by Cezary Kabala:
Many people complain about an excessive complication of the WRB rules and the number of qualifiers, and thus they request for simplification. But at the same time, we permanently receive the proposals of new qualifiers and new rules, sometimes from the same people... This is - in my opinion - the largest challenge for WRB: to simplify it after reaching its present maximum, or to extend it continuously?