Urbanisation is driving rapid declines in species richness and abundance worldwide, but the general implications for ecosystem function and services remain poorly understood. Here, we integrate global data on bird communities with comprehensive information on traits associated with ecological processes to show that assemblages in highly urbanised environments have substantially different functional composition and 20% less functional diversity on average than surrounding natural habitats. These changes occur without significant decreases in functional dissimilarity between species; instead, they are caused by a decrease in species richness and abundance evenness, leading to declines in functional redundancy. The reconfiguration and decline of native functional diversity in cities are not compensated by the presence of exotic species but are less severe under moderate levels of urbanisation. Thus, urbanisation has substantial negative impacts on functional diversity, potentially resulting in impaired provision of ecosystem services, but these impacts can be reduced by less intensive urbanisation practices.

中文翻译：

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城市化对鸟类功能多样性的全球影响。

城市化正在推动全球物种丰富度和数量迅速下降，但是对生态系统功能和服务的一般含义仍然知之甚少。在这里，我们将有关鸟类群落的全球数据与有关与生态过程相关的特征的综合信息进行了整合，以表明在高度城市化的环境中，这些种群的功能组成与周围自然栖息地相比平均具有20％的平均差异。这些变化的发生没有显着减少物种之间功能上的差异。相反，它们是由物种丰富度和丰度均匀度的降低导致的，从而导致功能冗余的下降。城市中本地功能多样性的重新配置和下降并没有因外来物种的存在而得到补偿，但是在中等程度的城市化水平下情况并不那么严重。因此，城市化对功能多样性具有重大的负面影响，有可能导致生态系统服务的提供受到损害，但是密集程度较低的城市化做法可以减少这些影响。