Taking the pulse of Earth's tropical forests using networks of highly distributed plots

https://doi.org/10.1016/j.biocon.2020.108849Get rights and content

Abstract

Tropical forests are the most diverse and productive ecosystems on Earth. While better understanding of these forests is critical for our collective future, until quite recently efforts to measure and monitor them have been largely disconnected. Networking is essential to discover the answers to questions that transcend borders and the horizons of funding agencies. Here we show how a global community is responding to the challenges of tropical ecosystem research with diverse teams measuring forests tree-by-tree in thousands of long-term plots. We review the major scientific discoveries of this work and show how this process is changing tropical forest science. Our core approach involves linking long-term grassroots initiatives with standardized protocols and data management to generate robust scaled-up results. By connecting tropical researchers and elevating their status, our Social Research Network model recognises the key role of the data originator in scientific discovery. Conceived in 1999 with RAINFOR (South America), our permanent plot networks have been adapted to Africa (AfriTRON) and Southeast Asia (T-FORCES) and widely emulated worldwide. Now these multiple initiatives are integrated via ForestPlots.net cyber-infrastructure, linking colleagues from 54 countries across 24 plot networks. Collectively these are transforming understanding of tropical forests and their biospheric role. Together we have discovered how, where and why forest carbon and biodiversity are responding to climate change, and how they feedback on it. This long-term pan-tropical collaboration has revealed a large long-term carbon sink and its trends, as well as making clear which drivers are most important, which forest processes are affected, where they are changing, what the lags are, and the likely future responses of tropical forests as the climate continues to change. By leveraging a remarkably old technology, plot networks are sparking a very modern revolution in tropical forest science. In the future, humanity can benefit greatly by nurturing the grassroots communities now collectively capable of generating unique, long-term understanding of Earth's most precious forests.

Resumen

Los bosques tropicales son los ecosistemas más diversos y productivos del mundo y entender su funcionamiento es crítico para nuestro futuro colectivo. Sin embargo, hasta hace muy poco, los esfuerzos para medirlos y monitorearlos han estado muy desconectados. El trabajo en redes es esencial para descubrir las respuestas a preguntas que trascienden las fronteras y los plazos de las agencias de financiamiento. Aquí mostramos cómo una comunidad global está respondiendo a los desafíos de la investigación en ecosistemas tropicales a través de diversos equipos realizando mediciones árbol por árbol en miles de parcelas permanentes de largo plazo. Revisamos los descubrimientos más importantes de este trabajo y discutimos cómo este proceso está cambiando la ciencia relacionada a los bosques tropicales. El enfoque central de nuestro esfuerzo implica la conexión de iniciativas locales de largo plazo con protocolos estandarizados y manejo de datos para producir resultados que se puedan trasladar a múltiples escalas. Conectando investigadores tropicales, elevando su posición y estatus, nuestro modelo de Red Social de Investigación reconoce el rol fundamental que tienen, para el descubrimiento científico, quienes generan o producen los datos. Concebida en 1999 con RAINFOR (Suramérica), nuestras redes de parcelas permanentes han sido adaptadas en África (AfriTRON) y el sureste asiático (T-FORCES) y ampliamente replicadas en el mundo. Actualmente todas estas iniciativas están integradas a través de la ciber-infraestructura de ForestPlots.net, conectando colegas de 54 países en 24 redes diferentes de parcelas. Colectivamente, estas redes están transformando nuestro conocimiento sobre los bosques tropicales y el rol de éstos en la biósfera. Juntos hemos descubierto cómo, dónde y porqué el carbono y la biodiversidad de los bosques tropicales está respondiendo al cambio climático y cómo se retroalimentan. Esta colaboración pan-tropical de largo plazo ha expuesto un gran sumidero de carbono y sus tendencias, mostrando claramente cuáles son los factores más importantes, qué procesos se ven afectados, dónde ocurren los cambios, los tiempos de reacción y las probables respuestas futuras mientras el clima continúa cambiando. Apalancando lo que realmente es una tecnología antigua, las redes de parcelas están generando una verdadera y moderna revolución en la ciencia tropical. En el futuro, la humanidad puede beneficiarse enormemente si se nutren y cultivan comunidades de investigadores de base, actualmente con la capacidad de generar información única y de largo plazo para entender los que probablemente son los bosques más preciados de la tierra.

Resumo

Florestas tropicais são os ecossistemas mais diversos e produtivos da Terra. Embora uma boa compreensão destas florestas seja crucial para o nosso futuro coletivo, até muito recentemente os esforços de medições e monitoramento tem sido amplamente desconexos. É essencial formarmos redes para obtermos respostas que transcendam as fronteiras e horizontes das agências financiadoras. Neste estudo nós mostramos como uma comunidade global está respondendo aos desafios da pesquisa de ecossistemas tropicais, com equipes diversas medindo florestas, árvore por árvore, em milhares de parcelas monitoradas a longo prazo. Nós revisamos as maiores descobertas científicas deste esforço global, e mostramos também como este processo vem mudando a ciência de florestas tropicais. Nossa abordagem principal envolve unir iniciativas de base a protocolos padronizados e gerenciamento de dados a fim de gerar resultados robustos em grandes escalas. Ao conectar pesquisadores tropicais e elevar seus status, nosso modelo de Rede de Pesquisa Social reconhece o papel chave do produtor dos dados na descoberta científica. Concebida em 1999 com o RAINFOR (América do Sul), nossa rede de parcelas permanentes foi adaptada para África (AfriTRON) e Sudeste Asiático (T-FORCES), e tem sido extensamente reproduzida em todo o mundo. Agora estas múltiplas iniciativas estão integradas através da infraestrutura cibernética do ForestPlots.net, conectando colegas de 54 países e 24 redes de parcelas. Estas iniciativas estão transformando coletivamente o entendimento das florestas tropicais e seus papéis na biosfera. Juntos nós descobrimos como, onde e por que o carbono e a biodiversidade da floresta estão respondendo às mudanças climáticas, e seus efeitos de retroalimentação. Esta duradoura colaboração pantropical revelou um grande sumidouro de carbono persistente e suas tendências, assim como tem evidenciado quais os fatores que influenciam essas tendências, quais processos florestais são mais afetados, onde eles estão mudando, seus atrasos no tempo de resposta, e as prováveis respostas das florestas tropicais conforme o clima continua a mudar. Dessa forma, aproveitando uma notável tecnologia antiga, redes de parcelas acendem as faíscas de uma moderna revolução na ciência das florestas tropicais. No futuro a humanidade pode se beneficiar incentivando estas comunidades locais que agora são coletivamente capazes de gerar conhecimentos únicos e duradouros sobre as florestas mais preciosas da Terra.

Résume

Les forêts tropicales sont les écosystèmes les plus diversifiés et les plus productifs de la planète. Si une meilleure compréhension de ces forêts est essentielle pour notre avenir collectif, jusqu'à tout récemment, les efforts déployés pour les mesurer et les surveiller ont été largement déconnectés. La mise en réseau est essentielle pour découvrir les réponses à des questions qui dépassent les frontières et les horizons des organismes de financement. Nous montrons ici comment une communauté mondiale relève les défis de la recherche sur les écosystèmes tropicaux avec diverses équipes qui mesurent les forêts arbre après arbre dans de milliers de parcelles permanentes. Nous passons en revue les principales découvertes scientifiques de ces travaux et montrons comment ce processus modifie la science des forêts tropicales. Notre approche principale consiste à relier les initiatives de base à long terme à des protocoles standardisés et une gestion de données afin de générer des résultats solides à grande échelle. En reliant les chercheurs tropicaux et en élevant leur statut, notre modèle de réseau de recherche sociale reconnaît le rôle clé de l'auteur des données dans la découverte scientifique. Conçus en 1999 avec RAINFOR (Amérique du Sud), nos réseaux de parcelles permanentes ont été adaptés à l'Afrique (AfriTRON) et à l'Asie du Sud-Est (T-FORCES) et largement imités dans le monde entier. Ces multiples initiatives sont désormais intégrées via l'infrastructure ForestPlots.net, qui relie des collègues de 54 pays à travers 24 réseaux de parcelles. Ensemble, elles transforment la compréhension des forêts tropicales et de leur rôle biosphérique. Ensemble, nous avons découvert comment, où et pourquoi le carbone forestier et la biodiversité réagissent au changement climatique, et comment ils y réagissent. Cette collaboration pan-tropicale à long terme a révélé un important puits de carbone à long terme et ses tendances, tout en mettant en évidence les facteurs les plus importants, les processus forestiers qui sont affectés, les endroits où ils changent, les décalages et les réactions futures probables des forêts tropicales à mesure que le climat continue de changer. En tirant parti d'une technologie remarquablement ancienne, les réseaux de parcelles déclenchent une révolution très moderne dans la science des forêts tropicales. À l'avenir, l'humanité pourra grandement bénéficier du soutien des communautés de base qui sont maintenant collectivement capables de générer une compréhension unique et à long terme des forêts les plus précieuses de la Terre.

Abstrak

Hutan tropika adalah di antara ekosistem yang paling produktif dan mempunyai kepelbagaian biodiversiti yang tinggi di seluruh dunia. Walaupun pemahaman mengenai hutan tropika amat penting untuk masa depan kita, usaha-usaha untuk mengkaji dan mengawas hutah-hutan tersebut baru sekarang menjadi lebih diperhubungkan. Perangkaian adalah sangat penting untuk mencari jawapan kepada soalan-soalan yang menjangkaui sempadan dan batasan agensi pendanaan. Di sini kami menunjukkan bagaimana sebuah komuniti global bertindak balas terhadap cabaran penyelidikan ekosistem tropika melalui penglibatan pelbagai kumpulan yang mengukur hutan secara pokok demi pokok dalam beribu-ribu plot jangka panjang. Kami meninjau semula penemuan saintifik utama daripada kerja ini dan menunjukkan bagaimana proses ini sedang mengubah bidang sains hutan tropika. Teras pendekatan kami memberi tumpuan terhadap penghubungan inisiatif akar umbi jangka panjang dengan protokol standar serta pengurusan data untuk mendapatkan hasil skala besar yang kukuh. Dengan menghubungkan penyelidik-penyelidik tropika dan meningkatkan status mereka, model Rangkaian Penyelidikan Sosial kami mengiktiraf kepentingan peranan pengasas data dalam penemuan saintifik. Bermula dengan pengasasan RAINFOR (Amerika Selatan) pada tahun 1999, rangkaian-rangkaian plot kekal kami kemudian disesuaikan untuk Afrika (AfriTRON) dan Asia Tenggara (T-FORCES) dan selanjutnya telah banyak dicontohi di seluruh dunia. Kini, inisiatif-inisiatif tersebut disepadukan melalui infrastruktur siber ForestPlots.net yang menghubungkan rakan sekerja dari 54 negara di 24 buah rangkaian plot. Secara kolektif, rangkaian ini sedang mengubah pemahaman tentang hutan tropika dan peranannya dalam biosfera. Kami telah bekerjasama untuk menemukan bagaimana, di mana dan mengapa karbon serta biodiversiti hutan bertindak balas terhadap perubahan iklim dan juga bagaimana mereka saling bermaklum balas. Kolaborasi pan-tropika jangka panjang ini telah mendedahkan sebuah sinki karbon jangka panjang serta arah alirannya dan juga menjelaskan pemandu-pemandu perubahan yang terpenting, di mana dan bagaimana proses hutan terjejas, masa susul yang ada dan kemungkinan tindakbalas hutan tropika pada perubahan iklim secara berterusan di masa depan. Dengan memanfaatkan pendekatan lama, rangkaian plot sedang menyalakan revolusi yang amat moden dalam sains hutan tropika. Pada masa akan datang, manusia sejagat akan banyak mendapat manfaat jika memupuk komuniti-komuniti akar umbi yang kini berkemampuan secara kolektif menghasilkan pemahaman unik dan jangka panjang mengenai hutan-hutan yang paling berharga di dunia.

Introduction

As the most diverse and productive ecosystems on Earth, tropical forests play essential roles in the carbon and water cycles and maintenance of global biodiversity. Tropical forest lands are also home to more than a billion people and thousands of cultures. Having first provided the environments and germplasm that sustained foragers and farmers since the earliest days of humanity, today they underpin a large fraction of our globalized diet and intense demand for water, food and clean air. They also affect our health in multiple ways, providing rich pharmacopoeias to traditional and modern societies, and capable of changing the course of history when pandemic zoonotic pathogens emerge as forests and wildlife are exploited. Tropical forests are also critical to determining the degree and impact of anthropogenic climate change. Because of their extent, carbon density and productivity, they may both slow global heating by absorbing carbon into their biomass and soils, or accelerate it as deforestation and high temperatures damage forests and release carbon to the atmosphere.

Tropical carbon and biodiversity are therefore critical targets for environmental measurement and monitoring. While vital to our past and future, efforts to measure and monitor them have until recently been localised and largely disconnected. Although aspects of their ecology can be sensed remotely, on-the-ground, tree-by-tree measurement is essential. Indeed ground measurements are irreplaceable – whether to address a plethora of ecological questions (e.g., Wright, 2021), inform and validate ecosystem models (e.g., Malhi et al., 2021), or assist with interpreting remotely acquired data (e.g., Chave et al., 2019; Duncanson et al., 2019; Phillips et al., 2019). Yet the very features that enhance tropical forests' ecological value, such as remoteness, diversity and high rainfall, make fieldwork challenging. Tropical forest science and scientists from forest-rich countries are often under-resourced and academically marginalised. Often colonized from afar and distant from economic centres, tropical nature and many who explore it remain peripheral to national and global academic and political priorities.

The focus of this paper is specifically about the power of new collaborative networks to transform tropical forest science – what we do, how we do it, and eventually who does it - to understand tropical forest functioning and dynamics over large temporal and spatial scales. Conceived and funded starting in South America in 1999 (RAINFOR, Malhi et al., 2002) and later adapted to Africa (AfriTRON, Lewis et al., 2009) and Southeast Asia (T-FORCES, Qie et al., 2017) our approach encourages international grassroots initiatives and links them with standardized field methods and data management. Now, with ForestPlots.net (López-Gonzalez et al., 2011, López-Gonzalez et al., 2015) we support multiple networks with cyber-infrastructure that enables tropical scientists to do together what was previously impossible alone. Providing tools to ensure tropical scientists can manage, share and analyse their data themselves, ForestPlots.net is a global platform where data originators are in control and free to collaborate, support, or lead as much as they like. However, while much has been accomplished the wider challenges still run deep. Our aim of supporting the best possible science within a model of equitable access to data and other resources remains as much an aspiration as a claim of achievements already made.

Here we first review how the continental networks and ForestPlots.net emerged, in terms of collaborators, institutions, people and plots. Next we focus on key scientific achievements of the combined networks, including a comprehensive understanding of the variation in biomass carbon stock, growth rates, and carbon residence time among continents. We also review multiple discoveries concerning large-scale changes over time, with insights emerging from highly distributed permanent plots that have transformed our understanding of the role that tropical forests play in the biosphere. Finally, we return to the challenges of building and sustaining long-term science networks in the tropics and outline key priorities for the future.

Section snippets

Network development

Tropical research plots that tag, measure, identify and follow forests tree-by-tree have existed for decades. They long precede any continental or global network, but no plot survives since before 1939 and few predate 1970. The earliest efforts were closely connected to the imperial and post-imperial projects of European nations. As such, these were largely motivated by questions of timber inventory and wood production, and only later diversity and wider ecological questions. The very first

Environmental representation

While it is not possible to intensively sample the whole tropical forest extent, in practice RAINFOR, AfriTRON and T-FORCES have managed to cover almost the entire climatic and geographic space across the humid tropics with permanent plots (Fig. 4a) as well as extensively sample the biome space of the terrestrial tropics except for semi-arid biomes (Fig. 4b). Within each continent coverage has been focused on the moist tropical lowlands with sampling extending into montane and drier forest

Discovery: forest ecology across the tropical continents

RAINFOR, AfriTRON and T-FORCES plots have generated ecological and biogeographical insights that have only been achievable via large-scale collaboration. RAINFOR has revealed that Amazonian forests differ substantially from one another, even those that share essentially identical climates. For example, basal-area weighted wood density of northeastern forests is 50% greater than that of southern and western forests. This reflects floristic differences (Baker et al., 2004a, Baker et al., 2009;

Discovery: tropical forest change

The single most significant scientific impact of these multiple permanent plot networks has been to transform our understanding of how tropical forests function in the Earth system.

As the most diverse and carbon-rich tropical biome, the fate of humid tropical forests will impact the future of all life on Earth. Until quite recently it was axiomatic that old-growth tropical forests are at equilibrium when considered over sufficiently large scales, and that any changes observed at smaller scales

Challenges and the future of tropical forest monitoring

Large-scale plot networks have not only made a series of crucial scientific discoveries and advances, but even more profoundly the Social Research Network model pioneered by RAINFOR since 2000 has influenced how the science itself is being done. Tropical ecology has undergone a remarkable shift from a small cadre of researchers working in one or two sites to a more globalized and decentralised process with greatly increased contributions from tropical scientists. This has been made possible by

Achievements, impact and potential

Despite the challenges, tropical forest science has come a very long way. Until recently, tropical ecology suffered from a massive data deficit. We had plenty of theory and conjecture, but few comparable observations over time and space to deductively put these ideas to the test or inductively generate new ones. Networks such as ForestGEO, RAINFOR, AfriTRON, and the wider ForestPlots community have contributed much to resolving this. By leveraging a remarkably old technology, forest plot

CRediT authorship contribution statement

All authors have contributed to ForestPlots.net-associated networks by leading, collecting or supporting field data acquisition, or implementing and funding network development, data management, analyses and outputs. O.L.P. wrote the manuscript with initial contributions from S.L.L., M.J.S. contributed new analyses, M.J.S., G.L.P. and A.L. helped prepare the figures, and all authors reviewed the manuscript with many suggesting valuable edits. O.L.P., T.R.B., G.L.-G. and S.L.L. conceived //www.forestplots.net

Declaration of competing interest

There is no conflict of interest.

Acknowledgments

This paper is a product of the RAINFOR, AfriTRON and T-FORCES networks and the many other partner networks in ForestPlots.net which support long-term forest science and monitoring across tropical countries. These initiatives have been supported by numerous people and grants since their inception. We are particularly indebted to more than one thousand four hundred field assistants for their essential help in establishing and maintaining the plots, as well as highly distributed rural communities

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