Integrated Task, sea cows extinction

I would be grateful for correction to my essay
The reading claims that sea cow which lived near the shore of Siberia became extinct due to some dim reasons. However, the lecturer finds all the ideas dubious and presents some evidence to refute them all
The author argues that the number of sea cows decreased as a result of overhunting by native people for the sake of food resource. Conversely, the lecturer brings up the idea that sea cows were enormous creatures with 9 meter long and 10 tons mass, also the population of native villages in Siberia was not too large to hunt this bulky animals dramatically, hence one sea cow can support their food for long time and there was no need for overhunting.
Furthermore, the reading passage holds the view that environmental disruptions diminished the population of kelp which is a source of food for sea cows and as a result the number of sea cows went down. On the contrary, the professor underlines the fact that if the disturbances really happened before the 1768 other parts of the ecosystems should got influences. For instance the population of whales should decrease too but fishing ships did not report any decreased process for whales, so we can conclude that kelp grew well.
Finally, the reading asserts that the arrival of the European fur traders should be another reason, since they got advanced weapons and killed large number of sea cows to make profit. In contrast, the speaker dismisses this issue due to the fact that the extinction might have been seen when the European arrived but already the number of sea cows was quite small, so it shows that the ongoing process of extinction happened long before the arrival of fur traders, and the reason of that former process should be consider as the main reason of extinction not the European.

TOEFL listening discussions: What will the student probably do with her next paper?

I found the reading and lecture:

Reading Part:
A huge marine mammal known as Steller’s sea cow once lived in the waters around Bering Island off the coast of Siberia. It was described in 1741 by Georg W. Steller, a naturalist who was among the first Europeans to see one. In 1768 the animal became extinct. The reasons for the extinction are not clear. Here are three theories about the main cause of the extinction.
First, the sea cows may have been overhunted by groups of native Siberian people. If this theory is correct, then the sea cow population would have originally been quite large, but hundreds of years off too much hunting by the native people diminished the number of sea cows. Sea cows were a good source of food in a harsh environment, so overhunting by native people could have been the main cause of extinction.
Second, the sea cow population may have become extinct because of ecosystems disturbances that caused a decline in their main source of food, kelp (a type of sea plant). Kelp populations respond negatively to a number of ecological changes. It is possible that ecological changes near Bering Island some time before 1768 caused a decrease of the kelp that the sea cows depend on.
Third, the main cause of extinction of the sea cows could have been European fur traders who came to the island after 1741. It is recorded that the fur traders caught the last sea cow in 1768. It thus seems reasonable to believe that hunting by European fur traders, who possessed weapons that allowed them to quickly kill a large number of the animals, was the main cause of the sea cow’s extinction.

Now listen to part of a lecture on the topic you just read about.
(male professor)
The truth is we don’t know what the main cause of extinction of Steller’s sea cow was. There are problems with each of the theories that you read about.
First, the sea cows were massive creatures. They were up to nine meters long and could weigh over ten tons, just enormous. A couple of sea cows could feed a small Siberian village for months. And the population of the native Siberian people wasn’t very large. So while the Siberians certainly did hunt the sea cows, they didn’t need to hunt a lot of them. So it’s unlikely they were the ones who brought the sea cows to the point of extinction.
Second, about a hypothetical decrease in kelp caused by ecological disturbances, well, if something severe really happened in the ecosystem near Bering Island sometime before 1768. it would have affected not just the kelp but also other parts of the ecosystem. For example, it would have caused the decline in other marine animals like whales. But fishing ships in the area did not report a whale decline. Since there is no indication of broader ecosystem problems, the kelp was probably growing just fine and the sea cows did not experience food shortage.
Third, it might seem like the European traders were responsible because the sea cows became extinct soon after the Europeans arrived. But, actually, by the time that the Europeans arrived, the sea cow population was already quite small. We have evidence that the sea cow population was at its largest hundreds of years before the 1700s. So something was causing a serious and on-going decrease in the sea cow population long before the Europeans arrived in the Bering Island area. Whatever this something was, it should be considered the main cause of the extinction, not the European traders who were just the last to arrive.

Hi Bestwayy, I think you have a good overall format here. You show a clear contrast between the reading and the lecture. You have captured all of the points of the lecture, but your explanations are not always natural and understandable - you have some errors in usage and some incorrect word choices. Overall, I would rate this a 3.5 out of 5.