Tansley from a ‘continental’ viewpoint

By Christian Körner, University of Basel, Switzerland.

Christian is one of Europe’s leading plant ecologists. He has been Professor of Botany in the University of Basel, Switzerland, since 1989.

In his writings Tansley always acknowledged the foundations of modern plant ecology lay in the books of Eugen Warming (1896),¹⁴¹ a Dane, and Andreas Schimper (1898), a Strasbourg-born Alsacien¹³². The first was on ecological plant biogeography, the second on the physiological basis of plant biogeography. These texts became more widely available across the channel in Britain when they were translated into English in 1909 and 1903, respectively. Tansley and his colleagues were about to fight the narrow curricula for botany in English universities, curricula leaning heavily on plant taxonomy and morphology. Tansley admired the new concepts laid out in these books; they exemplified what he referred to as 'wissenschaftliche Botanik' or scientific botany. He spoke of a 'new movement' among plant scientists that was based on evidence and logical argument. Tansley's own concepts and approaches to ecology, published several decades later, contained strong echoes of those earlier continental works. He changed what was formerly descriptive biogeography, or plant sociology, into what – with the help of later workers such as MacArthur,¹²⁴ Harper,¹¹⁸ Grime,¹¹⁴ and others - would become the new Anglo-American functional ecology.

On several occasions, including in his earliest accounts, Tansley recognized the value of the previous efforts of others to ‘inventory’ floras. It was, he believed, a necessary base - which did not have to justify itself by any theory but which required some standardization – that had to be built before ecology could enter the scene. He proposed that the next step was pattern finding, the recognition of patterns best represented by maps. He wrote, ‘Unintelligent description of badly selected things is worthless, but intelligent description of the right things...is indispensable to the progress of science...’,³⁹ and ‘...the basis of all science is to 'intuit', i.e. to make a direct mental picture of the contents of space and time’.¹¹

I find it remarkable how Tansley, even early in his thinking (when he was just 33 years old), defined ecology and emphasized that it was not an all inclusive study of any complex situation that involves different organisms. Thus, taking pollination as an example, he argued that while the interaction of a pollinator with a flower is not ecology, the adaptation of alpine flowers to special pollinators is.¹¹ In his view, ecology becomes what it is only through the inclusion of habitat conditions - what he termed the topographic aspect of life. This is where mechanisms come into play that explain the success of species in a given environmental matrix. In the sense of Schimper,¹³² Tansley translated this into topographic physiology, or what today we would call physiological ecology. He was clear that three steps are required to turn any plant ecological endeavour into a mechanism-oriented piece of science. We must ask, (1) what ? (make an inventory), (2) where ? (construct a map, and define habitat conditions), and (3) why/how is an organism thriving where it does ? (investigate the mechanism). Too often works get stuck in the second step or, worse, focus on the third step without having gone through the second. Adding the requirement to ask ‘why’ and ‘how’ was his explicit protest against the 'old' Botany and his motivation to found the NEW Phytologist: ‘...how things come to happen in the way they do - for that is the ultimate aim of science.’³⁹

Schimper was for the last two years of his life (1899-1901) professor of botany here in Basel. Sitting in 21st century comfort in what was once his office, it is hard to imagine the practical difficulties of working and traveling he faced over a hundred years ago. Schimper died at a young age from malaria, contracted in Central Africa during his third and last expedition. His travels had taken him as far as SE-Asia. Tansley too had his difficulties. Through a large part of the 1920s, he did not even have a proper job and was made professor in Oxford only when he was 56, long after he had founded two of today’s most prominent journals and helped found the British Ecological Society.¹¹⁶ Yet, somehow, in spite of their difficulties, the remarkable insights of these two men matured and bore fruit.

Scientific traveling from a young age was for Tansley, just as for me, the key that enabled him to ask the right general questions and to recognize recurring patterns. Impressed with what they saw on their journeys, both Schimper and Tansley adopted the comparative approach and looked for the large biogeographic patterns in the tradition of Alexander von Humboldt. In my view, there is no other ecology than comparative ecology. And both felt that biological sciences, part of which ecology inevitably is, needed to go beyond description and recording to ask the why and how questions.

Unfortunately, such questions are quite often narrowed down too far; this leads to detailed examinations which have rather limited potential for arriving at a broader understanding, simply because of a lack of larger scale comparisons. On several occasions, Tansley pointed to this potential problem in the practice of ecology and I strongly sympathize with his view. We see a lot of emphasis on isolated aspects that are unlikely to advance what we may now call ecological theory. We have the tools today for testing ecological hypotheses at a global scale, such as stable isotopes and geographical information systems, and the task of collecting comparative information worldwide and from electronic data bases was never easier. We should use these tools more often.

There is another aspect I like in Tansley's works, his dismay when terms are handled vaguely. He repeatedly pointed out how much fruitless debate is created by the unconstrained generation of terms. In his classic paper of 1935,⁵⁵ where he famously coined the term 'ecosystem' (by rejecting the 'complex organism' concept), he also fiercely attacked the climax concept for its vague meaning. Orderly handling of terminology in an intrinsically logical framework is particularly important in ecology, given its often inevitably 'soft' objects. For example, I think much confusion could have been avoided if terms like stress, limitation,¹²⁰, ¹²¹ and treeline¹²² had been properly defined; defined by what they mean and what they do not mean.

The furthering of ecological theory requires generalizations. These can emerge only from testing hypotheses about a given question in a multitude of habitats across a broad spectrum of environmental conditions. Nature offers wonderful, still undervalued, experiments that yield evolutionary answers that human experiments will hardly ever be able to reproduce. Schimper started to exploit these opportunities during his travels,¹¹⁹ and Tansley expanded this concept to all aspects of ecology, with a strong emphasis on community processes. I often wish his ideas would receive broader attention in the current global change experimental community. Why, for example, is anybody daring to warm an experimental plot rather than studying nature's sharp thermal gradients in situ, as they impressed Tansley on the occasion of his 1908 visit to the Swiss Alps under the guidance of his highly esteemed Swiss contemporaries C. Schröter and H. Brockmann?¹³³ This excursion impressed Tansley so much that he (successfully) suggested the foundation of the International Phytogeographical Excursions⁷² and afterwards frequently cited Schröter's works.

One of the Swiss participants in those early excursions, and a contemporaty of Tansley, was Helmut Gams. It was he who introduced me to the flora of the Tirol through the many excursions he offered at weekends - long after he had retired and when I was in my 20s. I can claim, therefore, another personal link to the early history of plant ecology.