5-2課文翻譯

原文：
Climate differences explain why one area of the earth's land surface is a desert,another a grassland, and another a forest and why there are different types of deserts, grasslands, and forests cause by global air circulation.

Figure 5-8 shows how scientists have divided the world into several major biomes-large terrestrial regions characterized by similar climate, soil, plants, and animals, regardless of where they are found in the world. The variety of terrestrial biomes and aquatic systems is one of the four components of the earth's biodiversity-a vital part of the earth's natural capital.

By comparing Figure 5-8 with Figure 5-2 and Figure 1 on pp. S12-S13 in supplement 4, you can see how the world's major biomes vary with climate. Figure 3-6 shows how major biomes in the United States are related to its different climates.

On maps such as the one in Figure 5-8, biomes are shown with sharp boundaries, each being covered with one general type of vegetation. In reality, biomes are not uniform. They consist of a mosaic of patches, each with somewhat different biological communities but with similarities typical of the biome. These patches occur mostly because the resources that plants and animals need are not uniformly distributed and because human activities remove and alter the natural vegetation in many areas.

Figure 5-9 shows how climate and vegetation vary with latitude and elevation. If you climb a tall mountain from its base to its summit, you can observe changes in plant life similar to those you would encounter in traveling from the equator to one of the earth's poles. For example, if you hike up a tall mountain in Ecuador, your trek can begin in a tropical rain forest and end on a glacier at the summit.

Differences in climate, mostly from average annual precipitation and temperature, lead to the formation of tropical (hot), temperate (moderate), and polar (cold) deserts, grassland, and forests.

翻譯：
氣候的差異解釋了地球地表為什麼一個區域會是沙漠、一個區域是草原或是一個區域是森林，且藉由全球空氣環流解釋了為什麼會有不同種類的沙漠、草原及森林。

圖5-8顯示科學家是以大陸地區中，有相同特性的氣候、土壤、植物、動物，並無論是在世界的哪裡發現，將世界分為數個主要的生物群落。各種各樣的陸地生物群落以及水生系統，是組成地球自然資本的一個重要部分─生物多樣性的四個要素之一。

比較圖5-8與圖5-2以及S12~S13中，補充教材4的圖1，你可以看到世界的主要生物群落是隨著氣候所改變的。圖3-6顯示，在美國的生物群落和氣候差異是有關聯的。

在圖5-8中，尖峭的界線顯示了每個生物群落都被覆蓋著一種常見的植被。事實上，生物群落並非完全一致的，在圖中的每個生物群落所組成的色塊中，都還是有一些不同類型的生物群集，但還是保有相同且典型的的生物群落。這些色塊的出現是很重要的，因為那些植物與動物資源並不需要一致的分散，也因為人類的活動將會遷移以及改變很多區域的自然植被。

圖5-9顯示氣候和植被隨著緯度及高度改變。如果當你爬山時，從山底爬到峰頂你將會注意到，那些植物的改變就如同你從赤道旅行至地球的任一極區一樣。例如，你徒步走上厄瓜多爾的一座高山，你的旅程將會起於山底中的熱帶雨林，最後結束於高山峰頂上的冰河。

氣候的差異之所以形成熱帶(熱)、溫帶(適度)以及極地(冷)般的沙漠、草原和森林，主要是來自於年雨量及年均溫。