Well, as I said before, you can find rock art all over the world, but I'd like to focus now on the rock art of the Aboriginal people of Australia.
正如我此前所言，全世界都有岩石艺术，但我想主要集中讲讲澳大利亚土著人的岩石艺术。
The images that survive in this part of the world span at least 20,000 years.
在这个地区留存下来的图像跨越了至少两万年。
In fact, the Aborigines were still practising this art form in the late 18th century, when the Europeans began to arrive, and certain images point to the contact between them.
实际上，土著人在18世纪晚期还在继续艺术创造，这时候欧洲人开始踏上澳大利亚的领土。画中的一些形象也指出了两者之间的联系。
For example, the Aborigines began to draw ships which they would have seen along the coast. It's hard for us to imagine what they must have thought when these first began to appear.
譬如，土著人开始描画他们所见的沿岸船只。我们很难想象，一开始出现船只的时候，土著人都会想什么。
Another image that is evidence of European arrival is that of horses: an animal that would have been very alien to the Australian landscape.
另一种形象是马，这能作为欧洲人到来的证据，（因为）马这种动物对澳大利亚来说是非常陌生的。
Um, it isn't actually known how many sites there are across Australia where rock art can be found, but unfortunately we do know that much of the art is being lost to us.
到底澳大利亚有多少地方发现了岩石艺术，人们尚未清楚，不幸的是，我们清楚了解已经遗失了多少艺术作品。
Erosion, of course, is one of the key reasons for its destruction, but human activity is also increasingly responsible.
当然了，侵蚀是艺术破坏的其中一个主要原因，但人类活动的影响也越来越大。
Since the 1960s, industry alone has destroyed around an estimated 10,000 pieces of art.
据估计，从20世纪60年代起，仅仅是工业就破坏了奖金一万件艺术作品。
At this rate, in 50 years, half of all Australian rock art could have disappeared for good.
按照这样的速度，50年内，一半的澳大利亚岩石艺术都会永远消失。
Vandalism is sadly another factor. And although most people, I believe, would wish to preserve this art, I'm afraid that tourism is another reason why the art is disappearing.
令人伤心的是，蓄意毁坏文物也是因素之一。尽管我相信，大多数人都希望能保护这种艺术，但我恐怕旅游业也是艺术消失的另一个原因。
In some cases, the art is damaged when...
在某些情况下，艺术被破坏…