Mark van Benthem, director and senior advisor

Telephone+31 317 46 65 60
Viewhis projects and publications

Of our director's duo, Mark is the one dealing with our external affairs. Acquisition, creative thinking, that’s his thing. And the interaction with people. In the meantime at Probos, he is 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. Always look at the impact of projects: does it contribute to good forest management, does it promote biodiversity, does it benefit the soil? Not surprisingly he is deeply involved in 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 has a good sense 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. Since the mid 1990’s, Mark is involved in the certification of sustainable forest management (SFM) and assists since 2008 various Dutch governmental agencies in design and implementation of their Sustainable Timber Procurement Policy (TPP). Mark has worked on the European Sustainable Tropical Timber Coalition (STTC) since its launch.

Jan Oldenburger, director and senior advisor

Telephone+31 317 46 65 74
Viewhis projects and publications

Forests and numbers, that's what Jan likes best. As half of our director's duo he deals with the finances, administration and other internal affairs. But in the meantime, he also likes to get his teeth into all possible forest and timber statistics, for the ministry, the Dutch Bureau of Statistics, the timber sector or any other person 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!"

Due to his extensive experience as National Correspondent for organizations such as FAO, ITTO and UNECE, Jan has a wide network within the international world of forests and wood, including the relevant government bodies. He is also member of ENFIN. His English therefore is good, and his German proficient.

Jaap van den Briel, senior advisor

Telephone+31 317 46 65 53
Viewhis projects and publications

Jaap is a forestry expert who likes to look at the forest from a socio-economic point of view. Rely on him to arrange things, lobby, and bring the right stakeholders together. He’s always looking for the interaction between forest and society. One day he is chairman of the core team ‘Forest and Wood’, a collaboration of 38 parties working on climate smart forestry. And the next day he is an inspector, trainer, or sets up supply chains for roundwood or woody biomass.

His favourite tree or forest? "The Scots pine. Such a beautiful architectural tree. Especially solitary, in drifting sand, when the branches grow all horizontally."

Jaap’s English is excellent and he can get around comfortably in French. He lived in Bhutan, Niger and Ruanda for years, working for the Ministry of Foreign Affairs and SNV as an advisor on (social) forestry and reforestation.

Martijn Boosten, senior advisor

Telephone+31 317 46 65 62
Viewhis projects and publications

Martijn is interested in everything. As long as it has to do with forestry and preferably is somewhat practical. 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 give an excursion or to make an inventory of cultural history. This yields an endless supply of knowledge, which he stores well. Does anybody want to know something about anything? Martijn instantly draws 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!"

As a board member of the European Pro Silva network for close-to-nature forestry, Martijn has developed a broad network of forestry experts all over Europe. He is an expert on woody biomass and bio-energy, afforestation and agroforestry, as well as the cultural heritage of forests. His English is excellent and he is proficient in German.

Joyce Penninkhof, advisor

Telephone+31 317 46 65 57
Viewher projects and publications

Joyce liked her job as study advisor at Wageningen University and Research well enough. But in the back of her mind she always thought: if Probos calls (where she once did an internship), I’ll consider leaving. And then we did call! We hired her in 2015 because of her broad interest and structured way of working, and now she works on all kinds of subjects. From practical fieldwork on invasive species to sustainable timber procurement policies. She also smoothly organizes an excellent international conference on sustainable sourced tropical hardwood. Where she deals with both content and all practicalities.

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 working experience in Finland. At Probos she organized international conferences on sustainably sourced tropical timber in Rotterdam, Aarhus (DK) and Paris. She is an expert on sustainable timber procurement policies and invasive species (particularly Asian Knotweed). Her English is fluent and she can get around comfortably in German.

Jasprina Kremers, advisor

Telephone+31 317 46 65 51
Viewher projects and publications

Jasprina stood out during 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 with us. She thought that was a great idea! She finds herself too practical for scientific research, and too curious for just practical work. So at Probos she is perfectly positioned right between knowledge development and practice. For example, she conducts a literature study into soil compaction by forestry machines. This way she contributes 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 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
Viewhis projects and publications

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 nice 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 a son of a gardener, he is no stranger to practice either. That is what attracted him in Probos: a beautiful 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 Amazone 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 does 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."