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 Suriname, 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.

Joyce Penninkhof, senior 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.

Guus Beerkens, advisor

Telephone+31 317 46 65 52

GIS, spatial statistics and remote sensing are the topics Guus likes to work on the most. LiDAR, drones, satellites and other "toys" he finds fantastic to work with. This also involves processing data, from writing scripts and models to creating beautiful maps and clear figures. Due to his studies in forest and nature management, the forest is also not an unfamiliar working environment. At Probos, he wants to combine all this in innovative ways to contribute to better forest management and information.

His favorite tree or forest? "Douglasses! Not because they are necessarily the most beautiful trees right now, but they are a great object of study for remote sensing."

During his internship at Probos, Guus conducted research on identifying individual trees from the AHN3 and predicting various tree parameters from it with field data.

Sietze van Dijk, advisor

Telephone+31 317 46 65 55

Sietze has more than 40 years experience in the forest sector and forest based industry, of which he worked and lived for over 20 years in the tropics, both in the Congo Basin and in the Amazon region, and now works at Probos since 2020. Before that, he and Probos already worked together at several projects related to certified sustainable forest management (SFM) and timber trade and the introduction of lesser known timber species (LKTS) in EU markets. In Suriname, in the early 2000, he was the first to facilitate the introduction of FSC certification in the country. Since then he is engaged in the SFM and CoC certification and the responsible sourcing of timber and timber products. In 2005 he co-founded the environmental consultancy firm 'Environmental Services & Support (ESS) to which he is still associated as a senior consultant in the field of environmental assessments, forest certification and related capacity building programmes for a wide range of international funding agencies. At Probos, Sietze shares his knowledge and experience and employs his network in support of the international profile of Probos. Part of his present work relates to data gathering and analysis on the impact of EUTR and FLEGT-VPA on EU timber markets and how this may contribute to the further increase of certified tropical timber trade globally.

His favorite tree or forest? "The ‘kankantri’ (Ceiba pentandra) in Suriname: A gigant that still can be seen everywhere in the open landscape and agricultural field as a solitary tree left standing due to its imputed cultural values as part of the traditional marrons’ beliefs”. “And of course the few and far between shrubs and trees in the semi-arid region of the Gash Delta in Sudan, where I learned to always think twice before cutting a tree, realising that its timber is the last it can provide for”."

As parttime consultant Sietze wil share his knowledge and experience within the Probos team and employ his netwerk in support of the international profile of Probos.

Gera op den Kelder, advisor

Telephone+31 317 46 65 54
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Gera did research on spontaneous forest development during her internship at Probos, in cooperation with the Ark Foundation. Her dedication and cooperation resulted in a nice evaluation of her internship and we asked her if she would like to continue working for us. She was quite taken with it! At Probos, she is committed to future-proof forest management and more forests and trees. Whatever the topic, she gets to work on it and is fully committed.

Her favourite tree or forest? "The weeping willow. Contrary to what the name suggests, I don't think the tree has something sad but something majestic with its size and hanging branches. For me there is a certain serenity."

Gera has also been passionate about football from an early age. Giving up is not an option and there is always room for improvement. She sees every situation to learn from and do better next time. This attitude does not only come in handy on the football field, but she also incorporates it into her work at Probos.

Gino van Maaren, advisor

Telephone+31 317 46 65 55
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Growing up between fruit trees, Gino already knew from an early age where his passion lay: trees and nature. During his study 'Forest & Nature Management' at the WUR he soon found out that he likes to advise in the everyday practice of forest & nature management. For his internship he looked at the use of rich litter species, non-native tree species and non-local origins as part of revitalization and climate smart forest management. This interested him so much that he wanted to pursue this further.

His favourite tree or forest? "The amber tree. When autumn arrives, an amber tree turns beautiful colors! When a tree has all the colors from green to yellow, orange, red and then purple, it's like looking at a fairy tale tree."

At Probos, Gino is concerned with future-proof and sustainable forest management and more forests and trees. This way he hopes to contribute to a green(er) Netherlands.

Bryndis Perdijk, advisor

Telephone+31 317 46 65 55
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After studying Forestry and Wildlife Management, with a specialization in tropical forestry, Bryndis worked for the past 10 years as an auditor and project leader at SKH, among other positions. She was also co-founder and secretary of STIP. At Probos she will mainly focus on the field of 'making chains sustainable and valuing forest ecosystem services', but we expect her to be able to strengthen the organization more broadly as well.

Her favourite tree or forest? "The Wallaba (Eperua falcata), a tree that stood near the house where I lived in Suriname. When I climbed Mount Voltz in Suriname for the first time at the age of 18 and looked out over the rainforest, it was such a beautiful experience that I would like to dedicate myself to forests."

Bryndis has worked in Suriname, Oceania and Ethiopia. In addition, she has an affinity for the wood industry through many visits to a variety of companies in the wood processing industry.

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.

Marleen van der Kolk, officemanager

Telephone+31 317 46 65 69

Marleen is our enthusiastic and creative office manager. She likes to regulate and organize and will do this by maintaining websites, design and secretarial work. This all to support the Probos team members. Marleen grew up in the forests of Wageningen and enjoys taking walks in this region. She hopes that through her work at Probos, she will contribute to more and healthier functioning forests.

Her favourite tree or forest? "The birch in our backyard! Beautiful in any season, offers shade on hot summer days and the garden birds can shelter from danger."