As North America rode out a summer of remarkable heat , fall foliage and cool, crisp weather still seemed like distant, alien concepts across much of the continent in early September 2026. But fall comes early in the tundra and subarctic ecosystems of Nunavut, in far northern Canada.
2026 年 9 月初，北美度过了一个异常炎热的夏季，但对于北美大陆的大部分地区来说，秋天的落叶和凉爽、清爽的天气仍然像是遥远而陌生的概念。但在加拿大最北部努纳武特地区的苔原和亚北极生态系统中，秋天来得较早。
Vivid signs of the season were already sweeping across the landscape on September 6 when the OLI (Operational Land Imager) on Landsat 9 captured this image (right) of the Coppermine River winding through low-growing shrubs and tundra vegetation upriver of Kugluktuk , a community at the river’s mouth. The other image (left) shows the same area on July 27, 2026, when vegetation was still green.
9 月 6 日，当 Landsat 9 上的 OLI（操作陆地成像仪）捕捉到这张照片（右）时，这个季节的鲜明迹象已经席卷了整个大地。另一张图片（左）显示的是 2026 年 7 月 27 日的同一区域，当时植被仍是绿色的。
The region is known for willow and birch shrubs, blueberries, bearberries, and other low-growing tundra plants that turn shades of red, orange, and yellow each fall. A NASA and South Dakota State University analysis of seven years of satellite data found that foliage in the region begins to change in early September and peaks in mid-month, making this one of the first places on the North American continent to change color. But blink and you might miss it: the analysis also showed that far northerly regions tend to have shorter periods of peak color—sometimes a week or less—compared to many lower-latitude areas.
该地区以柳树和桦树灌木、蓝莓、熊果和其他低矮的苔原植物而闻名，这些植物每年秋天都会变成红色、橙色和黄色。美国宇航局和南达科他州立大学对七年卫星数据的分析发现，该地区的树叶在九月初开始变化，并在月中达到顶峰，使这里成为北美大陆上最早变色的地方之一。但一眨眼，您可能会错过它：分析还表明，与许多低纬度地区相比，极北地区的峰值颜色周期往往较短，有时为一周或更短。
In the fall, leaves change colors as they lose chlorophyll, the molecule that plants use to synthesize food. Chlorophyll makes plants appear green because it absorbs the red and blue light from sunlight as it strikes leaf surfaces. However, chlorophyll is not a stable compound, and plants must continuously synthesize it, a process that requires ample sunlight and warm temperatures. As temperatures drop and days shorten in autumn, levels of chlorophyll fall as well.
秋天，叶子会因为失去叶绿素而变色，叶绿素是植物用来合成食物的分子。叶绿素使植物呈现绿色，因为它吸收阳光照射到叶子表面时发出的红光和蓝光。然而，叶绿素并不是一种稳定的化合物，植物必须不断合成它，这个过程需要充足的阳光和温暖的温度。随着秋季气温下降和白天缩短，叶绿素水平也会下降。
As concentrations of chlorophyll decline, the green fades from leaves, presenting an opportunity for other pigments— carotenoids and anthocyanins —to take the stage. Carotenoids absorb blue-green and blue light, so in the absence of chlorophyll, they cause leaves to appear yellow. Anthocyanins absorb blue, blue-green, and green light, so light reflecting off the pigments appears red. Citizen scientists have an opportunity to help NASA scientists track fall color and contribute to long-term environmental databases with the GLOBE North American Phenology Campaign . Participants observe and record leaf color changes during the spring and fall, helping scientists understand plant responses to climate and environmental changes.
随着叶绿素浓度的下降，叶子上的绿色逐渐消失，这为其他色素（类胡萝卜素和花青素）上台提供了机会。类胡萝卜素吸收蓝绿光和蓝光，因此在缺乏叶绿素的情况下，它们会导致叶子呈现黄色。花青素吸收蓝色、蓝绿色和绿色光，因此色素反射的光呈现红色。公民科学家有机会帮助 NASA 科学家追踪秋天的颜色，并通过 GLOBE 北美物候运动为长期环境数据库做出贡献。参与者观察并记录春季和秋季叶子颜色的变化，帮助科学家了解植物对气候和环境变化的反应。
NASA Earth Observatory images by Michala Garrison, using Landsat data from the U.S. Geological Survey . Story by Adam Voiland.
NASA 地球观测站图像，由 Michala Garrison 使用美国地质调查局的陆地卫星数据拍摄。亚当·沃伊兰的故事。