Mark van Benthem, director and senior advisor

Telephone+31 317 46 65 60
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As our director and senior advisor, 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 has been working 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 has been assisting the Dutch government on implementing its Sustainable Timber Procurement Policy. Since 2013 he has been supporting the Sustainable Tropical Timber Coalition as an 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.

Nienke Welle, senior advisor

Telephone+31 317 46 65 53
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Nienke studied Forestry at Van Hall Larenstein University of Applied Sciences and obtained a master’s degree in Landscape History at the University of Groningen. She gained experience at a forestry consultancy, the Federation of Private Land Ownership and as an independent consultant, project leader and researcher. Nienke has a background in developing smart forest function combinations that support the creation of new forests. In doing so, she pays attention to the balance between ecological, economic, and social interests in the countryside, and remains thoughtful of administrative relations. Nienke is also interested in natural and cultural heritage, especially the history of estate management.

Her favorite tree or forest? "An impossible question! I am fond of the typically Dutch small-scale cultivated landscape, with mature oaks or chestnuts surrounding the farms. But also, old beech forests, a poplar meadow with lush undergrowth, an avenue with American oaks in the autumn, the endless forests in the Black Forest."

At Probos Nienke is mainly involved in the field of 'More forest and trees'. Her ambition, together with partners in rural areas, is to contribute to the objective of 10% more forest in the Netherlands. You may contact Nienke for questions regarding forest expansion and associated issues related to spatial planning, financing, planting material and the Natural Beauty Act, but also for questions on forest history or historical geographical themes.

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 has been working 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 has been assisting 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.

Sander Teeuwen, advisor

Telephone+31 317 46 65 66
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Sander is just as crazy about numbers as his former mentor Jan Oldenburger. 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, where he investigated the effect of logging activities on the regeneration of tree species. His English is fluent and his German reasonable.

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. He has been working 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 giant 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 thing it can provide”."

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.

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 working experience 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.

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 interested in it! At Probos, she is committed to future-proof forest management and more forests and trees. Whatever the topic, she 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 rather something majestic with its size and hanging branches. For me there is a certain serenity to it."

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 as a learning opportunity to 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 the orchards, Gino already knew from an early age what his passion was: trees and nature. During his study 'Forest & Nature Management' at the WUR he quickly found out that he likes to consult 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 forest revitalization and climate smart forest management. This interested him so much that he wanted to pursue this further in his career.

His favourite tree or forest? "The amber tree. When autumn arrives, an amber tree shows 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.

Jasper Velthuis, advisor

Telephone+31 317 46 65 51
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Jasper studied Forest and Nature management at Van Hall Larenstein University of Applied Sciences and obtained a master’s degree in Forest and Nature Conservation at Wageningen University. After his studies, Jasper aimed for the right balance between research and practice. He saw plenty of opportunities for this at Probos! Jasper applied via an open application, after which it quickly became clear that he is an asset to the team. Jasper prefers to work on current topics and issues within forest management, such as climate-smart forestry. And of course, Probos is heavily involved in such topics.

His favorite tree or forest? “I am particularly fond of the boreal forests, such as the ones that you can find in Scandinavia. Especially in northern Sweden where you can still find old-growth forests with interesting forest structures and hints to the past; the whole region has a certain raw and idiosyncratic quality to it"

During his studies, Jasper gained experience in Sweden and Switzerland. For instance, he contributed to a research project on the climate sensitivity of European beech under climate change. Within Probos, he is currently involved in various topics before he will further specialize. In his spare time, Jasper likes to exercise and further develop in this. A quality that also translates to his work.

Sylvia Schalken, officemanager

Telephone+31 317 46 65 55

With roughly 40 years of working experience in a wide range of different functions, Sylvia has shown her worth. After working in psychiatry, communication, and being a manager in elderly care, she wanted to delve into a whole different field of work. Within Probos, Sylvia supports the consultants in the project management and communication department. She also ensures that everything runs smoothly within the office. Planning, organizing, and communicating is what she does best.

Her favorite tree or forest? "The giant sequoias she encountered on her travels throughout North America. "Between these trees you feel so insignificant; at that moment I realized how powerful and beautiful nature can be."

Sylvia likes to write. She usually does this for, or on behalf of others, except on her own online blog; there she publishes her own short story every week. Sylvia is also active on various writing platforms, and she is proficient in professional storytelling. “By telling stories, people can inspire each other. Therefore, I am delighted to bring the stories of Probos into the spotlight.”