经济学人下载:森林保护 激光雷达探测术

Forest conservation
森林保护

Lidartector
激光雷达探测术

How to tell if countries are cheating on their conservation commitments
如何判断一个国家在森林保护承诺上是否有舞弊行为

The wood and the trees
林地与树木

In an isolated forest in the Sivalik hills of south-western Nepal, intense sun beats down through the treetops.
位于尼泊尔西南部西瓦利克山脉一处偏僻的森林内,毒辣的阳光正从树冠强射而入。

A sweaty trek up a steep, rocky slope leads to a spot where a team of researchers is busy measuring the trees.
经过一段汗流浃背的艰难跋涉，登上一处陡峭怪石嶙峋的斜坡,到达一块区域,就可以看到一组研究人员正忙着对树木进行测量。

They are working for Forest Resource Assessment Nepal, a joint venture between the Nepalese and Finnish governments.
他们是尼泊尔与芬兰政府森林资源评估合资企业的工作人员。

Two global-positioning-system devices guide the researchers to their target.
凭借两套全球定位系统就可将研究人员带到目的地。

Once there, they use tape measures, callipers and a hand-held laser to measure the heights and girths of all the trees within a 500-square-metre plot.
到达目标后，在圈定好的500平方米区域内，他们用卷尺，测径规和手持激光设备对所有树木的高度和树围进行测量。

These measurements, and each tree's species, are recorded on a clipboard. One plot finished; 959 more to go.
测量结果及每棵树的品种都会被记录下来。一块区域测量完成后，他们还要转战其余的959块区域。

A classic piece of forestry, then.
这是当时的一种传统林艺技术，

Boots on the ground.
采用人力进行实地考察，

Specimens duly counted.
准确测量标本。

But this is a study with a twist, for its purpose is to calibrate a new approach to the subject—one that will gather information by the bucketload without the need to rely on quite so many boots.
但一项新的研究将会使现状产生飞跃的转变，其目标是针对该课题开创一种新的测量方法—即无须动用众多的人力物力就可收集到大量所需信息。

This new approach uses a technique called lidar.
这项新方法采用的技术称之为激光雷达术。

Like its cousins radar and sonar,lidar,works by broadcasting electromagnetic waves towards a target and then building up a picture from the reflection.
与雷达和声纳技术相似，激光雷达的工作原理是通过向目标发射电磁波然后根据反射波构建图像。

In the case of lidar, the waves are in the form of an infra-red laser beam.
拿激光雷达来说，其波形采用的是红外激光束。

And in the case of the forests of south-western Nepal,the target is the trees.
以尼泊尔西南部的森林为例，被测目标就是树木。

During a forest survey, an aircraft-borne lidar sweeps a beam that fires about 70,000 pulses a second over the canopy.
在森林探测过程中，载有激光雷达的飞机将每秒产生7万个脉冲的激光束向森林树冠进行扫掠，

A sensor on the aircraft records the time it takes to receive the backscattering of pulses, and that is used to compute distances to the forest canopy and to the soil beneath.
同时安装在飞机上的探测设备会记录收到脉冲反向散射波的时间，然后分别用于计算到树林冠部及到土壤的距离。

The result, when processed through the computers of Arbonaut, a Finnish natural-resource-management company, is a three-dimensional image of the forest that can be correlated with, and calibrated by, the efforts of the chaps with the tape measures.
经过芬兰自然资源管理公司的Arbonaut计算机进行数据处理后，便可生成与采用卷尺那帮家伙的测量结果相关并可校验的树林三维图象。

And that, in turn, can be used to estimate the amount of carbon stored in the plot examined, and extrapolated to calculate the carbon stored in larger areas of forest that have been scanned by lidar, but not measured with tapes.
接下来，它还能用于估算所测森林区域的二氧化碳储存量，以此类推，激光雷达所探测的更大片森林区域的二氧化碳储存量也可以计算出来，但用的可不是卷尺。

The point of the project, which should be completed by 2014,
该项目预计到2014年完成，

is to allow Nepal to participate in international carbon-trading schemes that pay poor countries with lots of trees not to cut them down.
其实际意义在于能够让尼泊尔参加国际碳交易计划。该计划向拥有大量树木的贫穷国家支付资金，以确保其树木不被砍伐。

The Reducing Emissions from Deforestation and Forest Degradation scheme agreed at the United Nations'climate-change conference in Cancún last December may eventually be worth $30 billion a year.
联合国气候变化会议去年12月在墨西哥坎昆就减少砍伐森林和森林退化产生的排放计划达成协议，确定每年最终可用于森林保护的资金达300亿美元。

Nepal wants a slice of that.
尼泊尔也想参与其中分得一杯羹。

Lidar monitoring may provide a way of making sure it is delivering on its side of the bargain.
激光雷达监测可能提供了一种方法，表明尼泊尔履行森林保护协议的决心。

Until a few years ago, assessing the amount of plant matter in a forest in a cheap and accurate manner seemed an insurmountable problem, according to Eric Dinerstein,
环保组织世界自然基金会也参与了尼泊尔激光雷达项目的研究。

chief scientist of the World Wide Fund for Nature, a conservation group that is also involved in the Nepalese lidar project.
其首席科学家埃里克说，几年前，采用经济和准确的方法对植被数量进行评估似乎还是一项无法解决的难题。

Although a woodland's area can be worked out from satellite photographs, that gives only a hazy idea of the mass of the plants growing there.
尽管林地的面积能从卫星图片上得到，但它只能给提供我们生长在那里的大片植物的粗略情况。

If Forest Resource Assessment Nepal and projects like it are successful, that will change.
如果象尼泊尔森林资源评估这样的研究项目能够取得成功，情况就会大有不同。

It will then be possible, with reasonable confidence,to pay REDD money out only to those countries that deliver the goods—or, rather, the trees—in sufficient, measurable quantities.
我们将有充分理由相信REDD计划拨出的资金可能只会流向那些能够提供货真价实，或更确切的说，树木充足且数量可测量的国家。