Mark van Benthem, director and senior advisor

Telephone+31 317 46 65 60
LinkedInMark van Benthem

As our director, Mark likes to think creatively and is solution-oriented. This, and the interaction with people, is what drives him. He is also our greatest idealist. With each project, he checks whether it makes the world a little bit better. If not, it’s a no-go, as far as he is 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 involved with topics such as sourcing sustainable timber and the relationship between forest management and biodiversity.

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

Mark gained international working experience in Suriname, Chile, Mexico, Peru, Canada, Ukraine, Indonesia, the Republic of Congo, Cameroon and Finland. Since the late nineties, he has been involved in certification of sustainable forest management (SFM) and has written lots of publications. For instance, he (co-)authored various books on forest history, forest management and biodiversity, and afforestation. Mark actively looks with partners for ways to increase the value of forests, thus contributing to forest conservation and forest expansion.

Nienke Welle, senior advisor

Telephone+31 317 46 65 53
LinkedInNienke Welle

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
LinkedInJoyce Penninkhof

During her internship at Probos, Joyce researched the cultural history of the Sint Jansberg. After a brief period working at WUR, she started at Probos in 2015. With her structured way of working, she deals with various topics, both content-wise and practically. Joyce is interested in anything related to sustainable forest management and is therefore a good source of information for colleagues. Learning from each other and continuing to take steps together in forest management, also for future generations of forests and people, is important to her.

Her favorite tree or forest? "The forest on the Sint Jansberg near Groesbeek; hilly and situated on an old estate. You will find deciduous forests, coniferous production forests, but also old ponds and other beautiful cultural-historical elements. It almost feels foreign."

Joyce gained international working experience in Finland, where she researched woody encroachment in peatlands. Within Probos, Joyce is mainly involved in the field of 'future-proof forest management'. Here, she works on topics ranging from grazing pressure research in which the quantitative effect of large ungulates on forest regeneration is recorded, to researching forest restoration and additional tree species. She also carries out research and is involved in projects on invasive exotic species (Asian knotweeds in particular) and is co-initiator of the Knowledge Network Invasive Exotic species. In addition, she gives various courses together with partner organizations.

Sander Teeuwen, senior advisor

Telephone+31 317 46 65 66
LinkedInSander Teeuwen

After completing his studies in Forest and Nature Conservation at Wageningen University, Sander started his career at Probos in 2018. He has since grown into an expert in forest inventories and co2 calculations, and is a source of information concerning forest and timber statistics. Gaining insight into the state and development of the (Dutch) forest and the timber market through data is central in Sander's work. However, as the son of a gardener, he is no stranger to the more practical side. That is what attracted him to Probos: a great 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 scattering through beautifully when the sun is shining. Also in the winter, when nobody else is outside."

Sander coordinates the field of data provision. By doing so, he contributes to the production of reliable statistics and market data in the field of forests and timber, which is essential for formulating policy and conducting proper research. Sander is the Netherlands' national correspondent for data provision for organizations such as the FOA, ITTO and UNECE, and is a member of the European National Forest Inventory Network (ENFIN). Sander also gained work experience in the Amazonian rainforest of Brazil, where he researched the effect of logging on the regeneration of tropical tree species.

Sietze van Dijk, advisor

Telephone+31 317 46 65 55
LinkedInSietze van Dijk

Sietze has been involved in the forest sector for some time, both in the Netherlands as well as far beyond. In the late 1990s, for example, he was at the basis of the Recognition Scheme for Forest Contractors (ErBo) and the first editions of the Arbo handbook and the Arbo information sheets in the Netherlands. He also worked in Suriname on the reconstruction of the Practial Center for the Forest and Nature sector and supervised the introduction of (FSC-certified) sustainable forest management there. Since then he has been closely involved in setting up certified timber trade chains and together with Probos he organized the first FSC trade mission to Suriname. Sietze has lived and worked in the tropics for over 20 years, namely in Nicaragua, Libya, Sudan, Democratic Republic of Congo and Namibia, besides Suriname. In 2005, together with a number of Surinamese colleagues, he founded the consultancy firm 'Environmental Services & Support' (ESS), in which he is still active as a senior advisor.

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 a parttime consultant, Sietze shares his knowledge and experience within the Probos team and uses his netwerk in support of the international profile of Probos.

Eli Prins, advisor

Telephone+31 317 46 65 74
LinkedInEli Prins

At Probos, Eli is involved in projects that focus on making the (tropical) timber value chain more sustainable, forest expansion, climate-proof forests, and ecosystem services. He likes to look for integrated solutions with partners, with a main goal of making a positive impact on forests. As a nature fanatic and birdwatcher, Eli can be regularly found in forests and nature reserves from large to small, with his binoculars and camera at hand.

His favourite tree or forest? The wet forest, such as the swamp forests in the dunes near Voorne and the alder forests near the St. Jansberg. Here, the mineral-rich groundwater and rich soils create a productive ecosystem where the diversity of plant and animal species can be immediately felt.

Eli has experience as a project manager of innovative projects and bringing together the 'triple helix', especially on themes within the circular economy and value chain collaboration. He also managed several deliveries of energy systems to Ukraine. He can put his work experience to good use in realizing impactful projects at Probos, by bringing different perspectives together in projects. He has completed two MSc courses; strategic entrepreneurship (EUR) and forest and nature management (WUR). During this last training, he acquired substantive knowledge about forests, including forest types and forest ecosystems, forest biodiversity, species identification, and forest management.

Gera op den Kelder, advisor

Telephone+31 317 46 65 54
LinkedInGera op den Kelder

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 was interested in working for us. She was interested in it! At Probos, she is active in the fields of  'future-proof forest management' and 'more forests and trees', but also works on projects concerning carbon, such as calculating carbon sequestration in trees and forests and carbon certificates. Whatever the topic may be, 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
LinkedInGino van Maaren

Growing up between the orchards, Gino already knew early on what his passion was: trees and nature. During his study Forest and Nature Conservation at Wageningen University he quickly found out that he likes to consult in the everyday practice of forest & nature management. For his internship he looked at utilising rich-litter species, non-native tree species and non-local provenances as part of forest revitalization and climate smart forestry. 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."

As an all-round advisor, Gino mainly focuses on the themes of 'future-proof forest management', 'more trees and forests' and invasive exotic species at Probos. From time to time he also assists in forest & timber statistics. In addition, Gino is interested in the role of urban forestry for biodiversity, climate adaptation and a healthy living environment.

Jasper Velthuis, advisor

Telephone+31 317 46 65 51
LinkedInJasper Velthuis

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 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.

Robin Zwijgers, advisor

Telephone+31 317 46 65 69
LinkedInRobin Zwijgers

Robin works as a consultant at Probos mainly in the field of data provision. He enjoys turning complicated datasets into insightful graphs and figures. Especially, when these datasets and figures aid the conversation about (the views on) forest management.

His favorite tree or forest? “A pine forest on sandy soils on a warm summer day. For me personally, an undervalued type of forest. A warm gust with the smell of sand and pine trees takes me back to holidays and camps of my youth.”

After his bachelor's degree, Robin chose something more suited to his interests: the Dutch forest. While studying Forest and Nature Conservation at the WUR, he noticed that he made the right call. After analysing the Dutch Forest Inventory (NBI) data, he wrote his thesis at Wageningen Environmental Research about forest ownership and harvest. During his internship at Bosgroep Zuid-Nederland, he improved the height growth function of a forest growth model using NBI data, completing his master's degree. His interests in the current affairs of Dutch forest management and his affinity for forest data provide a solid foundation for his activities at Probos.

Sylvia Schalken, officemanager

Telephone+31 317 46 65 55
LinkedInSylvia Schalken

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.”