and not enough to 疑问

only a handful of databases record the abundance of insects over a long time—and not enough to judge long term population trends accurately.

老师好，请问and 后只有一个副词enough吗？它的完整句子是什么样？

only a handful of databases record the abundance of insects over a long time—and not enough to judge long term population trends accurately.

they指代”“a handful of databases”

They arenot enough to judge long term population trends accurately.

用少数几个数据库去准确判断长期的种群趋势是不够的