思路解析：
1. 不要以为出现了时间变化就是动态图，此图为静态图;
2. 分段原则为：数据变化明显的一段，数据稳定的一段;
3. 重点描述极值和明显的数据：最大值，最小值，剧烈上升，下降，数据保持不变等等。
参考范文：
The graph shows the estimated maximum population of elephants in a range of Asian countries in both 1997 and 2004.
In most of the countries included in the graph, the population fell. This was most noticeable in Malaysia and Thailand, where the number of elephants was thought to be less than half the figure in 1997. In the former, the number of elephants dropped as low as 1000. India remained the country with by far the largest elephant population, but experienced a dramatic fall in numbers so that in 2004 there may have been as few as 7500. Despite its size, China had a very small population of at most 500 elephants by 2004.
Although the trend was downwards overall, elephant populations were thought to have remained stable in Laos and Vietnam at approximately 1200. The only country where elephants showed signs of recovering was Cambodia, where numbers may have risen by up to 200.
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