灭绝难题

在地球上人口已达60亿、而且个体消耗不断增加的情况下,我们在可持续利用自然资源领域正面临着巨大的挑战。有一个明确的指标来衡量任务的完成状况:那就是物种灭绝率。正因如此,我和同事一起统计了过去几年的鸟类灭绝率,还由此推断出未来几年鸟类的灭绝情况。

鸟类灭绝是了解人类对环境不可逆转的巨大影响的最好的窗口。全球10,000种鸟类当中的每一种背后,都可能有十种甚至百种其他不为人知的动植物、或者真菌类物种。鸟类分布之广意味着它们为物种的栖息地点和生存状况提供了无可比拟的信息来源。

对灭绝物种数量的估计差异很大,这是因为对物种总量的估计存在很大分歧,有人认为物种数量仅限于有学名的100万种,也有人认为物种数量竟能够高达1亿。为了避免上述不确定因素的影响,我和我的同事引入了灭绝率的概念¾也就是每个物种每年的灭绝数量,或者为了让数字更加合理,每百万个物种每百万年的灭绝数量¾ 用E/MSY来表示。除去已经发生的五大灭绝事件,化石记录表明大概的灭绝速度是每百万种生物每百万年有一种走向灭绝(1 E/MSY)。而具体到10,000种鸟类,每个世纪应该只有一种鸟类灭绝。

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