The Trillion Trees Initiative has garnered support from business and political leaders around the world. U.S. President Trump强调了主动性作为他保护环境计划的基石，对政府的罕见转变已转移到巴黎关于气候变化协议并拆除国内环境法规的协议。必威官网是真的吗来自双方的立法者还提出立法，以加速植树运动，包括“Trillion Trees Act" recently introduced by Rep. Bruce Westerman of Arkansas (which envisions increasing planting in the United States by 24 billion trees over 30 years).

If done well, planting trees can help address the climate crisis by removing carbon from the atmosphere (though it's no substitute for reducing greenhouse gas emissions) while providing benefits for communities and the environment. But how and where can the United States plant billions of new trees? The country can't realistically return productive agricultural lands to forest, not when we need to预计全球人口将达到100亿到2050年。我们也不能期望树木在不合适的景观上生长 - 认为沙漠或大平原 - 没有大量的水和肥料，这会带来自己的环境后果。

新分析从WRI表明，即使在这些极限范围内，美国也有足够的空间将树木恢复到当前重新种植率之外的景观 - 到2040年，如果我们在全国范围内使用所有合适的土地，而无需降低粮食生产，那么到2040年，最高可达600亿棵新树木。这些树木每年可以从大气中清除多达5.4亿吨二氧化碳，相当于该国年度净温室气体排放量的近10％，或美国农业的所有年度排放。

我们在哪里种600亿棵新树？

Here are five ways the United States can restore trees to the landscape:

1.造林项目可以恢复210亿棵树

造林涉及在历史悠久的林地上种植树木，这些土地不再支持森林覆盖物，包括受野火或疾病打扰的土地，以及郊区和农村地区的开放空间。这些景观中的许多可能不会自然地再生森林，或者可能需要很多年才能这样做，因此需要人类干预。

2.东部森林可以用240亿棵

Half of all U.S. forests used for timber are considered "understocked" by the Forest Service. Restocking forests, for example by replanting after timber harvests or controlling competition from invasive species, can store more carbon in existing forests — especially in the eastern United States, where wildfires pose a smaller risk.

3. Silvopasture Practices Can Add 13 Billion Trees

农民可以维持牲畜，同时将树木整合到牧场上。除了隔离碳外，Silvopasture系统还可以增加土壤的生育能力，减少牲畜的热应激，并提供木材，水果或坚果的补充收入。

4. Cropland Agroforestry Practices Can Incorporate 2 Billion Trees

Not all cropland is suitable for农林业，但是在某些地区，在田间或溪流周围或沿溪流之间种植树木的某些地区可以为农民提供大量的环境和经济利益，同时从大气中清除碳。

5. Urban Reforestation Initiatives Can Plant 400 Million Trees

The total number of trees cities can plant is small relative to opportunities in other places. But expanding tree cover in urban areas can also clean the air and provide a healthier quality of life for residents, while benefiting the climate by cooling urban "heat islands" and reducing energy demand for air conditioning in homes and businesses.

我们如何为植树工作提供资金？

The United States may not be able to plant 60 billion trees overnight, but it can start now. With a public investment of $4-4.5 billion per year — comparable to what the federal government currently spends on fossil fuel subsidies, but nearly 100 times more than what the Trillion Trees Act would provide — the country could complete this tree restoration campaign within 20 years. That investment would help private landowners shoulder the upfront costs of tree planting, which range from $50 to over $500 per acre.

公共投资可以以奖励树木修复的形式出现，以类似的土地所有者支付为基础，美国农业部问题为森林和农业用地的保护做法。投资还可以通过树木修复的税收抵免来实现，类似于太阳能的投资税​​收抵免。

Under either policy mechanism, the government could encourage small landowners to participate by making third-party intermediaries eligible for the subsidy. Intermediaries such as land trusts, private companies or local governments could engage new landowners, bring together landowners to lower transaction costs, and provide technical assistance — especially important for practices like silvopasture that involve complex management. Federal lawmakers could also leverage state and local policy tools, like smart growth plans or property tax incentives, by awarding federal grants to states that meet tree restoration targets.

How Will Tree Restoration Address Climate Change?

No matter how many billions of trees we plant, tree restoration is not a silver-bullet strategy to fight climate change. Scientists have shown that achieving the Paris Agreement goals and limiting the worst climate impacts means reaching净零温室气体排放around 2050. If the majority of the potential 60 billion trees are restored and grow to maturity, they could remove 7 billion tons of carbon dioxide cumulatively through 2050. But still more carbon removal will be needed from other natural and technological solutions to keep the United States on track: tree restoration would only provide四分之一或更少在2050年，该国每年都需要清除大约20亿吨二氧化碳。

但是作为一个"all-of-the-above" strategy这包括减少排放和去除碳，树木修复可以提供有意义的好处 - 这些好处远远超出了碳。美国的树木已经提供$6.8 billion in health benefits每年通过从空中过滤污染，除了清洁水，野生动植物栖息地和森林工业的额外好处。将树木恢复到景观确实是气候和社区的双赢，但是我们现在需要开始种植新树木，以便到本世纪中叶到达其全部碳驱动潜力。必威官网是真的吗为此，美国不仅需要谈论一万亿棵树。它需要在这个气候机会上投资数十亿美元。必威官网是真的吗

编者注：此博客文章的先前版本指出，在美国，Urban Reforestation可以占400,000棵新树。正确的数字为4亿。我们后悔错误。