passive voice

[goforenglish]

Hello,
I would like someone help me with these sentences in the Passive Voice. It seems hard to figure out what tenses to use. I mean should I use Past Simpe or Past Perfect as the things happened so many years ago.


Lots of thanks.

Twenty-five years ago 16 billion tonnes of carbon dioxide(CO2), the gas which causes the ‘greenhouse effect’, (release) …into the air by motor vehicles and industry in a year.
Next year 23 billion tonnes of CO2(probably/release)…and all the time the ozone layer, which protects the earth, (destroy)…by CFC*gases.

In 1974 56 million tonnes of fish(take)…from the earth`s oceans.
Since then the number of fish taken from the oceans(rise)…to 90 million tonnes a year.

In 1975 there were two million African elephants.
This year the number of African elephants(fall)…to 500000. The elephant is now one of thousands of endangered species which(seriously/threaten)… .

Twenty-five years ago 100000 sq.km of the earth`s rain forests(lose)… each year.
Now every year approximately 170000 sq.km of rain forest(destroy)… .

In 1974 the earth`s population was 3.84 billion.The earth’s population is now over 6 billion. Each year it(rise) … by 95 million.

[freezeframe]

This looks like homework.

[Tdol]

Use the same tenses as the original text.

[Raymott]

The ones with "rise" don't seem to work for me as an exercise to put the sentences into the passive voice. This seems more like an exercise to create the present perfect tense in either the active or passive, as appropriate.

[goforenglish]

I am not a teacher, I was trying to help somebody with her homework but it seems impossible for me to do it correctly. I was only looking for help, and as I am new here I wasn´t sure where to post it. I thought Ask a teacher is the right place to do it. I made it clear when I registered that I am interested in the English language and I am not a teacher.
Thanks a lot for understanding.

[goforenglish]

The task for the exercise in the Passive Voice is to complete with the correct Active or Passive forms of the verbs in brackets. I did the exercise and I would kindly ask someone to check it and see if it is OK.

Many thanks,
Lia


A third of the natural world(destroy) has been destroyed by human activity in the past twenty-five years.

Global warming

Twenty-five years ago 16 billion tonnes of carbon dioxide(CO2), the gas which causes the ‘greenhouse effect’, (release) were released into the air by motor vehicles and industry in a year.
Next year 23 billion tonnes of CO2(probably/release) will probably be released and all the time the ozone layer, which protects the earth, (destroy) will be destroyed by CFC*gases.

Fish

In 1974 56 million tonnes of fish(take) were taken from the earth`s oceans.
Since then the number of fish taken from the oceans (rise) has risen to 90 million tonnes a year.

Endangered species

In 1975 there were two million African elephants.
This year the number of African elephants (fall) has fallen to 500000. The elephant is now one of thousands of endangered species which (seriously/threaten) is being seriously threatened .

Rainforests

Twenty-five years ago 100000 sq.km of the earth`s rain forests(lose)were lost each year.
Now every year approximately 170000 sq.km of rain forest (destroy) are being destroyed.

Population

In 1974 the earth`s population was 3.84 billion.
The earth’s population is now over 6 billion. Each year it(rise) rises by 95 million.

[milan2003_07]

Twenty-five years ago 100000 sq.km of the earth`s rain forests(lose)were lost each year.
Now every year approximately 170000 sq.km of rain forest (destroy) are being destroyed.

I agree that "were lost" is OK in sentence #1, but still I'd like to know your opinion about "were being lost", which emphasizes duration.

In the second sentence I'm not sure about "are being destroyed" because the word "every" usualy requires a simple tense. So I'd choose just "are destroyed".

The earth’s population is now over 6 billion. Each year it(rise) rises by 95 million.

I like "rises" here, but probably "is rising" is also OK.