Nature conservation efforts often focus on rare species. Common and moderately common species, however, receive much less attention. Our analysis of occupancy change of flora using a grid survey in 1980 and a habitat mapping survey in 2000 in Northeast Germany revealed significant losses for most of the 355 modeled plant species. Highest losses were recorded for moderately common species. Plant species occurring in 20–40% of grid cells declined on average by 50% in 20 years, although there were some methodological uncertainties. We found no correlation between occupancy decline and Red List category, but habitat loss seems to be a main driver. We suggest to rethink conservation indicators by including previously common species in monitoring. Our approach to estimating trends, using the association of species to habitat types and occupancy–area relationships, can be applied to other regions with heterogeneous resurvey data, but it cannot replace urgently needed monitoring schemes.

中文翻译：

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中度常见的植物显示出最高的相对损失

自然保护工作通常集中在稀有物种上。但是，普通和中度普通的物种受到的关注要少得多。我们通过1980年的网格调查和2000年德国东北部的栖息地地图调查对植物群落的占用变化进行了分析，结果表明，这355种建模植物中的大多数均遭受了重大损失。记录中度常见的物种损失最高。尽管存在一些方法上的不确定性，但20年至40％的网格细胞中出现的植物物种在20年内平均下降了50％。我们发现占用率下降与“红色名录”类别之间没有相关性，但栖息地的丧失似乎是主要的驱动因素。我们建议通过将以前常见的物种纳入监测范围来重新考虑保护指标。我们估算趋势的方法，