Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:Nevertheless, even if the higher estimate is more realistic, the population of the Udzungwa red colobus is by no means secure; its range is very limited, its populations are fragmented and discontinuous, and the threats from further habitat loss and human disturbance continued undiminished (Rovero et al. 2012).
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