填空题
Andrena Gravida is the name of a wild bee declining in the
United Kingdom and the Netherlands. A {{U}}(31) {{/U}} of months ago the
recent drop in migratory bird populations was known, based on a study
{{U}}(32) {{/U}} in the Netherlands. Now there's more troubling news
from that part of the world: a study released today by the journal Science
reports that there's been a dramatic loss of {{U}}(33) {{/U}} among wild
bees over the past 25 years in Holland.
There's {{U}}(34)
{{/U}} to a 70% decline in the variety and {{U}}(35) {{/U}} of bee
{{U}}(36) {{/U}} in some areas in Britain. A loss of biodiversity is
more subtle {{U}}(37) {{/U}} an overall drop in absolute numbers of
{{U}}(38) {{/U}} or plants, but it's still {{U}}(39) {{/U}} a
problem because the {{U}}(40) {{/U}} species in an ecosystem, the more
the system {{U}}(41) {{/U}} on each one of them, and if disease or some
other {{U}}(42) {{/U}} wipes out a species, its function could go
unfilled. In the {{U}}(43) {{/U}} of bees, that {{U}}(44) {{/U}}
is to pollinate plants, both wild and crop plants. And {{U}}(45) {{/U}}
the authors of the study show, there's been a {{U}}(46) {{/U}} decline
in plants that were once pollinated {{U}}(47) {{/U}} the disappearing
bees. Indeed, it isn't clear {{U}}(48) {{/U}} came first, the plant
decline or the decline in bees. It's also not clear {{U}}(49) {{/U}} any
crops are in trouble, only that there's a potential for it if this trend
continues. It's also not clear {{U}}(50) {{/U}} it's happening. Climatic
changes caused by global warming are a possibility, but so is the destruction of
wild habitat in both countries, as population and industry both expand.