The world’s forests are under threat. As well as being logged for timber and cleared to make way for agriculture, rising global temperatures are causing more intense wildfires.

Re-forestation is essential in the fight against climate change and to protect biodiversity, but planting saplings by hand can be slow and labor-intensive.

In recent years, drones have begun to be used to drop seeds onto land deforested by wildfires; a company called Mast Reforestation, formerly DroneSeed, has applied this method in the western United States and beyond, and World Wildlife Fund has used specialized drones to restore rural bushland in Australia. But for a forest to regrow, dropped seeds have to get into the soil and germinate, and that can be a challenge.

Researchers from Morphing Matter Lab at Carnegie Mellon University, in Pennsylvania, might have an answer. Inspired by nature’s own design, the lab has created an “E-seed” carrier that is intended to be dropped by drones and drill into the soil. But remarkably, the carrier doesn’t need an energy source to drill into the ground — it’s made from a material that “self-drills” in response to rain.

Lab director Yao Lining and her colleagues looked at erodium seeds for inspiration. The seeds of this genus of plants have a coil-like “drill” that changes shape when wet, using a “tail” to prop itself up and push more effectively into the ground.

The team created a seed carrier based on the same principle, made from white oak wood that naturally responds to changes in humidity. They chemically treated the wood to make it more flexible when wet, as well as softer and denser so it expands more effectively. Erodium has a single tail, but the seed carrier has three, making it easier to drill into soil.

According to research Yao published in the journal Nature, the carrier has an “80% drilling success rate on flat land,” making it more effective than erodium seeds in the same conditions. After the carrier burrows, the seed is protected from animals and the natural elements, improving its chances of germination.

So far, Morphing Matter has only tested the seed carriers at sites in Pittsburgh and Changxing, China, but Yao says the lab has received interest from venture capitalists and government agencies around the world wanting to use the seed carriers in reforestation projects.

But she notes that specific types of seed carriers must be developed for different locations, to accommodate different soils and humidity levels, amongst other variants. “We have to tailor the design to local conditions and the seeds of their interest,” explains Yao.(SD-Agencies)

Words to Learn 相关词汇

【砍伐森林】kǎnfá sēnlín deforest cut down or destroy trees in an area

【属】shǔ genus biological classification ranking between family and species

除了伐木和开荒种地，全球变暖还引发更猛烈的山火，这些因素都威胁着世界上的森林。

应对气候变化和保护生物多样性，植树造林至关重要，但人工植树费时又费力。

近年来，人们开始使用无人机将种子撒到野火毁林的空地上；一家名为

“桅杆造林”（前身为“无人种子”）的公司已经在美国西部以及其他地区有过类似尝试，世界野生动物基金会也曾使用无人机来恢复澳大利亚乡村烧毁的林地。但是，要让森林重新生长，播撒的种子必须钻进土里发芽，这并不容易。

宾夕法尼亚州卡内基梅隆大学变形物质实验室的研究人员给出了可能的答案。受大自然的启发，该实验室设计了一种基于橡木吸湿性的机器人（以下简称E-seed），由无人机投放，能自行钻入土壤。令人称奇的是，E-seed不需要动力就能钻入地下，因为特别的材料在雨水作用下能“自主钻孔”。

实验室主任姚力宁和她的同事从牻牛儿种子中找到了灵感。这种植物的种子有一个线圈状的 “钻头”，遇湿会改变形状，用 “尾巴”把自己撑起来，更有效地钻入地下。研究小组基于同样的原理设计了一个种子载体，由白橡木制成。他们对木材进行了化学处理，使其遇湿时延展性更好，更柔软、致密，能更有效地膨胀。牻牛儿只有一条尾巴，而E-seed有三条尾巴，更容易钻入土壤。

姚力宁在《自然》杂志上发表的研究报告称， E-seed“在平地上的钻孔成功率高达 80%”，在相同条件下，它比牻牛儿种子更高效。钻入地下后，种子受到保护，不会受动物和外界环境的影响，提高了发芽率。

到目前为止，变形物质实验室只在匹兹堡和中国长兴县的一些地方对E-seed进行了测试，但姚力宁说，世界各地风投和政府机构都表示对项目感兴趣，希望在植树造林时使用种子载体。

她指出，不同地点使用的E-seed必须量身定制，以适应不同的土壤类型和大气湿度，也要考虑其他变量。

她解释说：“我们必须根据当地条件和对方感兴趣的种子类型进行设计。”

(Translated by Debra)