The ecologist revealing the invisible networks that revive rainforests
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In a research station in central Panama, you can walk through a century of forest time, watching scrubby plots of adolescent trees give way to cathedral-like canopies of mature growth. Forest ecologist Daisy Dent, a senior scientist at ETH Zurich, oversees this sequence of plots across the Barro Colorado Nature Monument, some of which date as far back as the 19th century. Not one of the trees she surveys was planted by human hands. She maps, measures, and tracks each trunk that emerges, revealing how waves of tree life rise from bare earth.
在巴拿马中部的一个研究站，你可以漫步于百年的森林时光中，看着灌木丛生的幼树林地逐渐演变成如大教堂般宏伟的成熟林冠。苏黎世联邦理工学院的高级科学家、森林生态学家黛西·登特（Daisy Dent）负责监管巴罗科罗拉多自然保护区（Barro Colorado Nature Monument）内的一系列样地，其中一些样地的历史甚至可以追溯到19世纪。她所调查的每一棵树都不是由人类亲手种植的。她对每一棵破土而出的树干进行测绘、测量和追踪，揭示了树木生命如何一波又一波地从贫瘠的土地上崛起。
Tropical forests like these are our planet’s biggest terrestrial carbon sink, accounting for around 40% of carbon stored on land. As part of an international network of researchers, Dent is deciphering the networks of animal and plant interactions that enable some forests to recover after destruction. The goal is a low-cost, high-impact alternative to typical carbon-crediting schemes, which plant huge areas with a single species of tree. For over a decade, her research has built a body of evidence that such large “monocrop” programs could be expensive mistakes—and that more resilient forests can rebound naturally in just a few decades, re-creating ecosystems that suck up vast quantities of carbon dioxide.
像这样的热带森林是我们星球上最大的陆地碳汇，约占陆地碳储存量的40%。作为国际研究网络的一员，登特正在破译动植物间的相互作用网络，正是这些网络使一些森林在遭到破坏后得以恢复。其目标是为典型的碳信用计划提供一种低成本、高影响力的替代方案，因为那些计划通常会在大片区域内种植单一树种。十多年来，她的研究积累了大量证据，表明这种大规模的“单一作物”项目可能是昂贵的错误，而更具韧性的森林只需几十年就能自然恢复，重新创造出能够吸收大量二氧化碳的生态系统。
Few places are better to demonstrate this than Barro Colorado, a reserve covering the forested peninsulas and islands that formed when construction of the Panama Canal flooded the area in 1914. Under the management of the Smithsonian Tropical Research Institute, generations of ecologists have amassed more than a century of records. That means Dent can trace why some plots rebound after clear-cutting for farming and forestry while others falter. Fruit-eating animals—including spider monkeys, bats, and parrots—are responsible for planting more than 70% of trees in tropical forests, and Dent’s dataset can tell which built each patch of trees by depositing seeds in their nutrient-rich droppings.
巴罗科罗拉多是展示这一点的绝佳地点，该保护区覆盖了1914年巴拿马运河建设导致该地区被淹没后形成的森林半岛和岛屿。在史密森尼热带研究所（Smithsonian Tropical Research Institute）的管理下，几代生态学家积累了超过一个世纪的记录。这意味着登特可以追踪为什么有些样地在因农业和林业被砍伐后能够恢复，而另一些却陷入停滞。食果动物——包括蜘蛛猴、蝙蝠和鹦鹉——负责种植了热带森林中超过70%的树木，而登特的数据集可以通过分析它们在营养丰富的粪便中留下的种子，辨别出是哪些动物构建了每一片树林。
Many of these creatures worked together to plant a diverse 70-year-old patch whose canopy is approaching the stunning structure and richness of an ancient jungle. In contrast, a patch of similar age populated by narrow trunks of a single long-lived species, Gustavia superba, hints that tropical rodents called agoutis are more or less the sole animal architects behind this more homogeneous forest. The data she collects helps write a playbook for when to let ecosystems regenerate and when to give them a helping hand. One 2024 estimate in Nature found that some 215 million hectares of forest worldwide (an area larger than Mexico) could regenerate naturally.
许多生物共同努力，种植了一片拥有70年历史的多样化林地，其林冠结构和丰富度正接近原始丛林的惊人水平。相比之下，另一片同样树龄的林地却长满了单一长寿树种——古斯塔维亚木（Gustavia superba）的细长树干，这暗示着被称为刺豚鼠的热带啮齿动物几乎是这片更为单一的森林背后的唯一动物建筑师。她收集的数据有助于编写一份指南，指导何时应让生态系统自然再生，何时应施以援手。2024年《自然》杂志的一项估计发现，全球约有2.15亿公顷的森林（面积超过墨西哥）可以自然再生。
“Tropical forests are underpinned by this massive network of interactions,” Dent says—interactions between life-forms like the fungi that help trees take up nutrients, as well as pollinators and seed-distributors. Supporting those relationships is key to growing forests that lock up carbon and help sustain local communities and wildlife. Filling in the gaps Just over a decade ago, as the landmark Paris Agreement was being codified in 2015, forest recovery seized global attention as a solution to the climate crisis. Global leaders rallied behind plans to regrow a trillion trees, after the ecologist Thomas Crowther highlighted their potential to capture a decade’s worth of global carbon emissions.
“热带森林是由这种巨大的相互作用网络支撑的，”登特说，这些相互作用存在于各种生命形式之间，例如帮助树木吸收养分的真菌，以及传粉者和种子传播者。支持这些关系是培育能够固碳并帮助维持当地社区和野生动物生存的森林的关键。填补空白：十多年前，随着2015年具有里程碑意义的《巴黎协定》被编纂，森林恢复作为应对气候危机的解决方案引起了全球关注。在生态学家托马斯·克劳瑟（Thomas Crowther）强调了种植一万亿棵树在捕获十年全球碳排放方面的潜力后，全球领导人纷纷支持这一计划。
But the biggest question has lingered: How, exactly, do you regrow two trees for every star in the Milky Way? While startups have proposed seed-spraying drones and nutrient-coated seed bombs, Dent has spent two decades studying what happens when we let forests rebuild themselves. As a PhD student around the turn of the millennium, she researched old-growth forests in northern Borneo but felt hopeless watching entire landscapes felled for palm油 plantations. Rather than despair, she turned to restoration. Then, as a postdoc in 2005, she joined Panama’s Prorena, a joint initiative between the Smithsonian Tropical Research Institute and the Yale School of Forestry and Environmental Studies, which aimed at determining how best to establish diverse native forests on clear-cut land.
但最大的问题依然存在：究竟该如何为银河系中的每一颗恒星重新种植两棵树？虽然初创公司提出了种子喷洒无人机和营养涂层种子弹，但登特花了二十年时间研究当我们让森林自我重建时会发生什么。在千禧年之交作为博士生时，她研究了婆罗洲北部的原始森林，但看着大片景观因棕榈油种植园而被砍伐，她感到绝望。她没有陷入沮丧，而是转向了生态修复。随后，在2005年作为博士后，她加入了巴拿马的Prorena项目，这是史密森尼热带研究所与耶鲁大学林业与环境研究学院的一项联合倡议，旨在确定如何在被砍伐的土地上最好地建立多样化的原生森林。
Back then, secondary forests—ones that grow naturally after the original forest was lost—had been “a bit of a niche research area,” Dent says. But as farming and human infrastructure have driven deforestation, resurgent forests now account for some 70% of all tropical canopies. Prorena initially followed the usual playbook of transplanting nursery trees to rangelands, but Dent began to question whether planting was necessary. In 2009, she published an encouraging paper showing that animal populations rebound quickly as forests naturally regrow. In 2010, she began working in Barro Colorado on the plots established by the pioneering American ecologist Julie Denslow.
登特说，当时次生林——即原始森林消失后自然生长的森林——还只是“一个相当冷门的研究领域”。但随着农业和人类基础设施建设导致森林砍伐，复苏的森林目前已占所有热带林冠的70%左右。Prorena最初遵循了将苗圃树木移植到牧场的常规做法，但登特开始质疑这种种植是否有必要。2009年，她发表了一篇令人振奋的论文，表明随着森林自然再生，动物种群会迅速恢复。2010年，她开始在巴罗科罗拉多工作，研究由美国先驱生态学家朱莉·登斯洛（Julie Denslow）建立的样地。
In 1994, Denslow identified plots that had been regenerating naturally for 20 to 100 years, and Dent would add younger ones to continue the sequence. The site provides not just general data on forest regrowth but in-depth demographic information over time, says Robin Chazdon, a professor emeritus of ecology and evolutionary biology at the University of Connecticut who collaborated with Denslow when she established the plots. “It tells you more about the actual processes that are happening in the site,” she says. For example, previous research had shown that fast-growing “pioneer trees,” the first to thrive in the damaged land, are eventually overtaken by larger carbon-storing trees.
1994年，登斯洛确定了那些已经自然再生20到100年的样地，而登特则增加了更年轻的样地以延续这一序列。康涅狄格大学生态学与进化生物学名誉教授罗宾·查兹登（Robin Chazdon）曾与登斯洛合作建立这些样地，她说，该地点不仅提供了关于森林再生的通用数据，还提供了随时间推移的深入人口统计信息。“它让你更了解现场正在发生的实际过程，”她说。例如，先前的研究表明，在受损土地上最先繁茂的速生“先锋树”，最终会被更大的固碳树木所取代。
Dent’s research helped fill in gaps about the mechanics of how this happens—or doesn’t happen—in individual cases. In the Gustavia-dominated patch, for instance, stubborn grasses planted by cattle ranchers smothered most other trees before they could take root. These trees can hang around, crowding out the light, for 150 years, blocking the second wave of large-trunked trees. To plant or not to plant Dent found herself well placed for the massive influx of interest in reforestation that began in 2015. She’d
登特的研究有助于填补关于这一过程在个案中如何发生——或为何不发生——的机制空白。例如，在以古斯塔维亚木为主的林地中，牧场主种植的顽固草类在其他树木扎根之前就将其扼杀。这些草类可以存在150年之久，遮挡阳光，阻碍第二波大树干树木的生长。种植还是不种植？登特发现自己处于有利地位，能够应对2015年开始的对植树造林的大规模兴趣浪潮。她曾……