The Earth could be on the brink of the sixth mass extinction in history, claim scientists.

科学家声称，地球可能要迎来第六次大规模物种灭绝。

They believe that the steep decline in populations of many animal species, from frogs and fish to tigers, is as fast as any of the last five extinctions in the past 540 million years.

他们认为，近年来，许多动物物种数量的急剧减少，像青蛙、鱼类和老虎等等，其锐减速度赶得上过去5亿4千万年以来五次大规模物种灭绝的任意一次。

That would require dealing with a perfect storm of threats, including habitat fragmentation, invasive species, disease and global warming.

科学家们认为，物种灭绝速度现在因栖息地的破坏、外来物种的入侵、疾病的增多和全球变暖而加速，这些问题亟待解决。

Biologists estimate that within the past 500 years, at least 80 mammal species have gone extinct out of a starting total of 5,570 species.

此前，生物学家们对过去500年间的物种灭绝速度进行了深入的统计，至少有80种哺乳动物和5570种生物灭绝了。