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Focus on research: biologist Antoine Cleef

Photo: Bob Bronshoff

On 20th July 2006 Professor Antoine Cleef, a member of the Institute for Biodiversity and Ecosystem Dynamics (IBED), was awarded the ‘Orden de San Carlos’ for his research on biodiversity in Columbia and for his contribution to education in that country. He spent many years carrying out research on the Columbian páramos, grasslands high up in the Andes Mountains. He discovered about three hundred new plants, fifteen of which have meanwhile been named after him and now bear the name Cleefii. Officially, Professor Cleef has retired, but in practice there is little evidence of this!

The Columbian Orden de San Carlos; Professor Cleef still isn’t quite sure exactly which saint is referred to, but it is clearly an honour to receive the medal. ‘It is a token of appreciation from the government. I worked in Columbia for 35 years, carrying out research on the biodiversity there, and collaborating in development of education. During various expeditions that I organised together with colleagues, I concentrated on the vegetation in areas that had not been investigated previously. In the course of the years I have gradually increased my knowledge of the area and so now I know a reasonable amount’, says the researcher modestly.

Hidden city

The aim of Cleef’s expeditions was to document equatorial mountainous ecosystems. ‘For example, we climbed a mountain we wanted to chart and every hundred metres higher up we described everything we observed. We looked at the biodiversity of vascular plants, mosses, crust mosses and mushrooms, and also of soil fauna such as worms and insects. The type of rock, soil characteristics and the structure of mountainous forest and páramos were also documented.’ Cleef visited many different mountains in Columbia and didn’t only find unknown plants. ‘In some places we discovered a significant number of palms, often a sign that an area was once inhabited by people. We discovered one such place deep in the woods where the foundations of a hidden city lay under the forest canopy. We were the first to visit after all that time.’

Cleef experienced all sorts of things on expeditions with his students. ‘We tried to chart soil usage precisely, using radar images taken by airplanes or satellites which show the contours of the Amazon forest border clearly and show how much forest has been felled. Subsequently, these images need to be calibrated on the ground. As you can imagine, the people who grow coca aren’t too happy if you come along and measure their fields.’

Mega diverse

Cleef explains that, besides taking aerial photographs, there are various other ways to divide a landscape and subsequently classify the vegetation. ‘You start by staking off a test strip of, say, one square metre in open terrain. You then register all the various species you can see in this strip. Then you double the size of the strip and count all the species you didn’t see previously. And then you continue until you don’t find any more new species.’ Choosing the first test strip and the direction in which the test strips are enlarged must be done objectively and in the same type of vegetation. ‘Some investigators cast rings, and then take measurements where the ring lands. The researcher plots the number of species found against the number of test strips, so that a curve is formed that gives information about the species diversity in the region. If you carried out this test on the beach, for example, you’d be finished after one test strip, since not very much grows there at all.’

In the Netherlands there are about 1500 different species of plants. ‘My successor Joost Duivenvoorden investigated an area in Columbia the size of the province of Utrecht, and found about 7500 different species growing there’, says Cleef. ‘That is one of the reasons that Columbia is so interesting to investigate; we are trying to find an explanation why and how this came to be in the course of the past few millions of years. The country has an enormous biodiversity and is known as one of the ‘mega diverse’ countries.’

Another way to classify an area is to lay down a long strip and to count the number of plants of the various species under it. In this way you can determine the frequency with which certain plants occur. It is also possible to make a test strip and to examine the plant coverage. This method can be used, for example, in a wood, where various layers of vegetation grow. ‘You first look at the top tree layer, then at the second tree layer, at the tallest shrubs, at the lower shrubs and then at the plants low down on the ground. There are also plants growing on other plants, e.g. moss. Altogether it is possible to find coverage of more than 100% since the layers cover each other. You need to correct for that, but I think it provides insight if the coverage is more than 100%, since you then know that there is a layered growth in that area.

Practical application of science

Photo: Bob Bronshoff
‘Our research started out as a pure scientific search for knowledge. We went there with the aim of obtaining knowledge about the diversity of vegetation and flora in Columbia. However, the investigation has meanwhile attained more practical applications. For example, I used our knowledge to advise the government as to which areas could be nominated as national parks. We also look at the effects of reduction of biodiversity on erosion. Farmers set fire to land so that their livestock can graze on the protein-rich grass which then grows. The result is that, as grazing increases, the biodiversity decreases enormously and the bare land is no longer able to function as a sponge for the two to four metres of rain which falls annually, so that enormous floods occur. And …. drinking-water will become problematic.’ Restoration of all these degraded ecosystems is a challenge for the future.


At present, about ten Master’s students from Ecuador and Columbia are studying in IBED’s tropical research group, where Professor Cleef works. ‘They carry out the theoretical part of their study in Tropical Ecology here, and do the practical work at home. At the end of August, about 15 students were awarded their MSc diploma. The standard of these foreign students is very high: of the four students who graduated with honours, three came from South America. The student exchange programme is good for both Columbia and for the Netherlands. We are good in tropical ecology at IBED, where a school has been set up. We have achieved these good results by collaborating with researchers in Columbia and publishing together with them.’

Cleef has always been curious about the world around him. ‘I lived in Northern Limburg, and knew exactly what kinds of animals and plants were to be found on the heath there. Even still this is one of the things I like best about my work: the excitement and the challenge of carrying out research. It is nice being able to work with people who are have the same interest. Life in the open air is also a challenge, doing work that an office boy doesn’t to, the climbing and physical exertion. You need to persevere in difficult circumstances in order to obtain the data you are looking for.

Exciting moments

Cleef has experienced many tense moments. ‘I remember that we were in a tent at 4000 metres, dripping wet, with the lightning flashing around us continuously. It didn’t often happen, but we had lost our way. And that with the guerrilla all around. On another occasion we walked for miles through the Amazon forest in the pitch-dark night in thunder and heavy rainfall, looking for our boat. We saw soil-borne fungus become fluorescent as we shuffled across it - it lights up in the dark. It gave the same sensation as flying high above lighted cities at night. Splendid! But the high mountains, the Sierra Nevada del Cocuy with equatorial snow, made the biggest impression on me. The combination of all those special plants, the stem-rosettes, cushion plants, mosses and the snow was very special indeed. I would love to show that to my children some time. I took both of them to Columbia, but we were unable to visit that area because of the guerrilla.’


As well as speaking fluent Spanish and publishing in Spanish, Professor Cleef has also adopted more Columbian customs. ‘I think that the Latin-American influence is noticeable in personal interaction - I shake hands more readily. I am also very sensitive to the language and the culture, especially the music from those countries. I really enjoy a salsa or a joropo!
Although Professor Cleef retired recently, he can still often be found at IBED. ‘I am now writing the last book (of a series of seven books) Studies on Tropical Andean Ecosystems, I also give lectures, write articles and would like to make a glossy book about the páramos for the interested layman. I am also supervisor to five PhD students. In short, I’ll be hanging around here for quite a bit yet!,’ says Cleef, laughing.