Mark van Benthem, director and senior advisor

Telephone+31 317 46 65 60
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Of our directorial duo, Mark deals with external affairs. Acquisition, creative thinking, that’s his thing. And interaction with people. He is also our greatest idealist. With each project, he checks whether it makes the world a little better. If not, it’s a no-go, as far as he’s concerned. He always weighs up the impact of projects; does it contribute to good forest management, does it promote biodiversity, does it benefit the soil? Unsurprisingly, he is deeply committed to the cause of sourcing sustainable timber.

His favourite tree or forest? "Chilean Patagonia. In an afternoon you can cycle from the temperate rainforest on the coast, to above the tree line. Uphill you come across forests with alerce, the largest tree in South America, which grows very slowly and can be thousands of years old."

Mark is a forest and nature management graduate of the University of applied sciences Van Hall Larenstein and works at Probos since 2002. Since the late nineties, he has been involved in certification of sustainable forest management (SFM) also in his previous work at Face the Future and FSC Netherlands. Over the years Mark has developed a large network within the SFM community and the timber value chain. Since 2008 he assists the Dutch government implementing its Sustainable Timber Procurement Policy. Since 2013, he supports the Sustainable Tropical Timber Coalition as expert.

He (co-)authored a large number of articles in professional magazines and practical forest management books, covering topics like the relation between forest management and biodiversity, cultural heritage and afforestation. Mark has a good grasp of languages. His English is fluent, and his Spanish and German good enough to teach courses. Mark has international experience in Chile, Mexico, Peru, Canada, Ukraine, Indonesia, the Republic of Congo, Cameroon and Finland.

Jan Oldenburger, director and senior advisor

Telephone+31 317 46 65 74
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Forests and numbers, that's what Jan likes best. As the other half of our directorial duo he deals with the finances, administration and other internal affairs. But he also likes to get his teeth into every type of forest and timber statistic. He works with the government, the Dutch Bureau of Statistics, the timber sector and anyone else looking for figures on forests or timber. But don’t call him a nerd! He also runs practical projects, coaches young colleagues and prefers to work outside.

His favourite tree or forest? "An old douglas fir, sturdy, can take a beating. Wonderful the way you can look up the trunk! Beautiful!"

Jan started his career at Probos in 2004 after completing his study forest- and nature management at the Wageningen University. Since then he has worked in the field of forestry- and timber trade statistics, has performed a large number of market studies on several topics (e.g. biomass, share of sustainable timber on the market, waste wood) and wood flow analysis. Due to his extensive experience as National Correspondent for organizations such as FAO, ITTO and UNECE, Jan has a wide network across the global forest and wood scene, including in relevant government bodies. He is also a member of the European National Forest Inventory Network (ENFIN). His English is good and German proficient.

Martijn Boosten, senior advisor

Telephone+31 317 46 65 62
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Martijn is interested in everything. As long as it has to do with forestry and is preferably practical in some respect. Whether it’s about forest history, sustainable timber procurement, agroforestry, invasive species control, biomass or climate-smart forestry, he likes to leave his desk to go into the woods. For example, to prepare a field test, to lead an excursion or make a cultural history inventory. The result, an endless supply of knowledge, which he accesses at will. Does anybody want to know something about anything? Martijn instantly pulls an article or book from his archive!

His favourite tree or forest? "The Ravensbos near Valkenburg. A mixed forest, old, full of cultural history. I used to come there as a child. I saw the ranger on horseback, with a hat and a shotgun, and I thought: I want to be a forester!"

Martijn has a master’s degree in Forest and Nature Conservation from Wageningen University and works at Probos since 2006. Martijn’s main expertise is on climate smart forestry, afforestation, agroforestry, biomass and invasive species. He is one of the key experts on short rotation coppice in the Netherlands. Martijn also has a special interest in cultural heritage in forests and has worked on several research projects on this topic.

Martijn (co-)authored more than a hundred articles in professional magazines on forest management related topics. He is also a co-author to several practical forest management books, which are used in professional education. Since 2007 Martijn is a board member of Pro Silva Netherlands, an organization promoting close-to-nature-forest management. As a member of the European Pro Silva network Martijn has developed a broad network of forest management experts all over Europe. His English is excellent and he is proficient in German.

Joyce Penninkhof, advisor

Telephone+31 317 46 65 57
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Joyce studied the bachelor and master Forest and Nature Conservation at Wageningen University. During her master she gained working experience in Finland and at Probos as an intern. After graduation in 2012 she worked at the communication department of Wageningen University and since 2015 she works at Probos.

Her favourite tree or forest? "The forest on the Sint Jansberg near Groesbeek. Hilly, on an old estate. You come across deciduous forest, production pine forest, but also old ponds. It almost feels foreign."

Joyce has a broad interest and at Probos she works on all kinds of subjects. She is an expert on invasive species, mainly Japanese knotweed, and sustainable timber procurement policies. Joyce organizes the yearly conference of the Sustainable Tropical Timber Coalition, gathering participants from all over Europe to share knowledge and experiences. Since 2016 she assists the FSC group manager of the Dutch FSC certified group of forest owners. Her English is fluent and she can get around comfortably in German.

Jasprina Kremers, advisor

Telephone+31 317 46 65 51
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Jasprina stood out in her study of forest and nature management. The moment she finished her graduation presentation in 2017, we asked her if she wanted to apply for a job. She thought that was a great idea! She finds herself too practical for scientific research, too curious for just practical work. So at Probos she is perfectly positioned where knowledge development meets practice. For example, she conducts a literature study into soil compaction by forestry machines, contributing very practically to more sustainable forest management.

Her favourite tree or forest? "A fully grown, ancient English oak. I have seen a lot of them in Scotland, solitary in the open field. Magnificent!"

Jasprina has an MSc in forest and nature conservation and started working at Probos soon after her graduation in 2017. During her studies, Jasprina was already actively involved in the Dutch forest management sector and graduated on the topic of climate adaptation in forest management. At Probos, Jasprina is engaged in a wide diversity of projects on e.g. agroforestry, climate smart forestry and monitoring in the framework of the FLEGT Action Plan and the European Timber Regulation. Her English is good and her German proficient.

Sander Teeuwen, advisor

Telephone+31 317 46 65 66
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Our youngest addition, Sander is just as crazy about numbers as his mentor Jan. He simply gets a lot of satisfaction from digging through large datasets and drawing neat conclusions from them. So it’s hardly surprising we asked him to come to work with us to collect, analyze and transfer data immediately after his graduation. As the son of a gardener, he is no stranger to practical work either. That is what attracted him to Probos; a perfect combination of research, practice and knowledge transfer.

His favourite tree or forest? "The old open beech forest on the Oostereng near Wageningen, with the light falling through beautifully when the sun is shining. Even in the winter, when nobody else is outside."

Sander has working experience in the Brazilian Amazon rainforest, investigating the effect of logging activities on the regeneration of tree species. His English is fluent and his German reasonable.

Gebca Velema, secretariat, graphic design and dtp

Telephone+31 317 46 65 69

Years ago she started as our IT specialist, and now Gebca runs our entire office. She builds and manages all our websites, but also tackles administrative work, statistics and the layout of websites, invitations and anything else necessary. If you ask Gebca something, consider it done. She is flexible and always ready to help everyone.


Her favourite tree or forest? "The Speulderbos, also known as 'forest of the dancing trees'. The beautiful crooked, entwined trees with the light falling through. The old trees that are left to decay."