Natural succession is known to be the most cost-effective way of habitat restoration in the tropics. However, disturbed ecosystems with adverse soil conditions, such as clay quarries, necessitate intervention in the form of soil amelioration. To overcome this problem in the reclaimed Hambalang clay quarry, we will explore the potential of the giant milkweed Calotropis gigantea as a soil ameliorant. This native ruderal weed, which grows ubiquitously in Hambalang quarry’s barren areas, is known for its ability to tolerate a wide array of environmental conditions, its role in heavy metal phytoremediation and as a pollinator attractant, as well as its economic value as a source of biofuel, traditional medicine, and natural fiber. It also has potential in safe-site creation, enhancing germination and facilitating the reintroduction of native flora species for an accelerated natural succession. We will investigate the characteristics of C. gigantea’s growing environment in post-mined plots by examining mycorrhizal association with its roots, the presence of soil mesofauna, soil physicochemical properties, and heavy metal content in its tissue. The findings will guide the implementation of a cost-effective reclamation of Hambalang clay quarry, promote Indocement as an innovative rehabilitator of biodiversity, engage the local community by showing the economic and societal benefits of biodiversity, and contribute to the scientific community.

Video: Future Applications (Interviews with Dr. Yekti Asih Purwestri and Dr. Tri Rini Nuringtyas)

In this film, I talk to Dr. Yekti Asih Purwestri and Dr. Tri Rini Nuringtyas about Calotropis gigantea's potential beyond the quarry. While this may be the end of Lelly and Retno's project, I will be continuing to post more content on the project's YouTube channel ( and my Flickr ( Thank you everyone for supporting this project!

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Video: Reflections on Data Collection (Retno & Najmi interviews)

In this film, Retno and Najmi, a field assistant, share their experiences in Hambalang quarry. Each also provides their own perspective on the project, while Najmi goes on to compare the quarry with another harsh environment where Calotropis gigantea is known to thrive (more on that soon!).

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Photos: Data Collection (Part 2)

View the second part of our photography series on data collection, this time featuring more of Hambalang's plant and insect diversity, as well as the team's research in the quarry. Be sure to also check out the remaining images of this series on Flickr (

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Photos: Data Collection (Part 1)

You've seen the films, now view the photographic component of our series on data collection, featuring insects and toads, Calotropis gigantea up close, the team hard at work, and a project leader close to collapse from the unrelenting heat.

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Video & photos: Delivering a progress report

Lelly, Retno, and I converged on Bogor to deliver a progress report, and I managed to capture a small glimpse of the excitement. Watch the short film or read on to view the pictures.

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Video: Data Collection (Part 2)

From sore shoulders to broken tools, the second part of our series on data collection shows just some of the challenges we encountered, and more importantly, why hard lessons are sometimes the most valuable ones to learn.

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Video: Data Collection (Part 1)

The work was hard, but educating the public on Hambalang quarry's condition, biodiversity, and restoration need not be. Settle in and enjoy the first of two films on data collection in the quarry!

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Behind-the-scenes of the film on data collection

With the new film almost complete, have a look at some of the ideas and work behind it. As the longest film yet, a ton of work went into creating a cinematic and narratively sensible documentary that is also thematically consistent with the previous films.

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Our SPORETACULAR findings on AMF spore density and diversity

I'm happy to report our findings on arbuscular mycorrhizal fungi (AMF) spore density and identification. Among our three habitat types, spore density was significantly higher in the rhizospheres of Calotropis gigantea and Pennisetum polystachion than in bare ground. Meanwhile, six species from three families were observed, with Acaulosporacea being the most abundant. Please read on to see our results in more detail!

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Through the ocular lens: photography of mesofauna specimens is complete

There's always something special about being able to see the minutest details of an organism through a microscope, to the point that whilst photographing mesofauna specimens I couldn't help stopping every now and then to reflect on the what I was seeing. Ultimately, a total 32 vials' worth of specimens was photographed to aid with identification, and I hope you'll enjoy viewing a few of the more stunning images!

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Observations of mycorrhizal colonization: the preliminary results are here!

The preliminary results for Calotropis gigantea arbuscular mycorrhizal fungal (AMF) colonization are in, and they provide tantalizing evidence of the plant's potential as an indigenous soil ameliorant.

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Assessment of arbuscular mycorrhizal fungal colonization: laboratory work

Our Calotropis gigantea and Pennisetum polystachion root samples were processed for arbuscular mycorrhizal fungal (AMF) colonization observations.

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Photos: Surveying (Retno's picks)

Here are my favourite pictures from our first day in Hambalang quarry. As they show, we got a valuable reminder of the hardiness of Calotropis gigantea and its early successional species brethren.

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Photos: Surveying (Lelly's picks)

Yesterday, Joaquim posted some of his favourite pictures from our first day at the quarry. These are mine!

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Photos: Surveying (Joaquim's picks)

Accompanying our film on the first day at Hambalang quarry are a selection of images that shed further light on our experience. Here are five that particularly stood out to me. (Also read on to view a few others that didn't make the cut!)

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Video: Surveying

In this latest film, we survey our study area and look at two other sites that represent its past and potential future. We also discover that Calotropis gigantea is not limited to unreclaimed land - it can already be found growing spontaneously in an active site, highlighting why this plant has the potential to be central to a cost-effective and innovative restoration strategy that also fits within HeidelbergCement's guidelines for restoration in Asia and Oceania.

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Behind-the-scenes of the next film

After a few tough weeks of writing, recording, and editing, the next part of the project's film series is complete. We will be posting it soon, so in the meantime, have a look at what the process looked like behind-the-scenes.

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Video: Introduction

In this first video, we introduce the plant of interest, Calotropis gigantea, and give you a quick look at the environment and landscape of Hambalang quarry, as well as the biodiversity found therein.

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Laboratory work begins (and reflections on the environment and what we found)

Having returned home, the next step of our research is lab work on our samples. Soil, root, and leaf samples have been sent to their respective laboratories, and work has begun on mesofauna extraction. While we wait for the results, I think we can reflect on our experience in the field. Unlike reclaimed land, the abandoned quarry we chose to study was harsh, uncompromising, and devoid of any trees or tall shrubs to shelter us from the scorching sun. Surprisingly, however, fauna were still drawn...

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Calotropis gigantea data collection is complete, stay tuned for our documentaries of the experience!

We're heading home, but we have a ton of video and photos to show you. Not content with simply writing about our experience in Hambalang, we documented every step of the research, with team member interviews and more. Stay tuned!

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