Caribou lichens, Cladonia () spp., are a slow-growing, vital winter forage for caribou that are likely to be influenced by global warming. However, the large-scale response of caribou lichens to changing global climate remains unclear. Here, we derived caribou lichen cover maps for two time periods ∼30 years apart (i.e., the late 1980 s, and 2020 s) using Landsat satellite imagery for a region (0.59 million km) in Eastern Canada that includes all or portions of several boreal caribou population ranges. We restricted our assessment to regions with at least 10% lichen cover and evaluated differences between the two time periods. Results show that since the 1980 s satellite-derived lichen cover declined in 62% of the region evaluated, remained constant in 27%, and increased in 11%. Twenty-three percent of the lichen cover decrease occurred in areas that burned after 1980, while 77% of the decrease remains unexplained, with warming-induced shrub encroachment, and caribou presence and grazing both possible causes. Caribou lichen regeneration occurs within regions burned before the 1980 s. Given that shrubification and wildfire frequency are projected to continue increasing, further monitoring of the scale and scope of ongoing changes will help to clarify future patterns. However, our results strongly suggest that the amount of caribou lichens has declined overall.

中文翻译：

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卫星检测到过去三十年加拿大东部驯鹿地衣 Cladonia (Cladina) spp. 覆盖面积减少

驯鹿地衣 (Cladonia () spp.) 是驯鹿生长缓慢、至关重要的冬季饲料，可能会受到全球变暖的影响。然而，驯鹿地衣对全球气候变化的大规模反应仍不清楚。在这里，我们使用加拿大东部一个地区（59 万平方公里）的 Landsat 卫星图像得出了两个相隔 30 年的时期（即 1980 年代末和 2020 年代）的驯鹿地衣覆盖图，其中包括几个地区的全部或部分北方驯鹿种群范围。我们将评估范围限制在地衣覆盖率至少为 10% 的地区，并评估了两个时间段之间的差异。结果显示，自 20 世纪 80 年代以来，卫星来源的地衣覆盖率在所评估的区域中有 62% 下降，27% 保持不变，11% 增加。23% 的地衣覆盖减少发生在 1980 年之后发生火灾的地区，而 77% 的减少仍然无法解释，变暖引起的灌木侵蚀、驯鹿的存在和放牧都是可能的原因。驯鹿地衣再生发生在 20 世纪 80 年代之前被烧毁的地区。鉴于灌木化和野火频率预计将继续增加，进一步监测持续变化的规模和范围将有助于澄清未来的模式。然而，我们的结果强烈表明驯鹿地衣的数量总体上有所下降。