树木对我们很重要，因为它能防止水土流失，防沙，给我们新鲜空气。但现在乱砍乱伐的人太多了，使得树木的数量不断减少。我想我们应该出台有关保护树木的法律来保护这些对我们非常重要的树，我们还要去种树，并一代一代坚持下去
參考答案:The trees are very important to us because they are holding the water and soil, defending the sand, and bringing us fresh air. But now too many excessive disafforestation made the trees incessantly getting less. I think we should have law to protect the trees. Also we should plant trees and hold it generationally because the trees are really very very important to us.
把最后两句换了一下, 觉得这样更好点.