1 . City trees grow faster and die younger than trees in rural forestry, a new study finds. Over their lifetimes,then, urban trees will likely absorb less CO2 from the air thah forest trees.
As we all know, the earth would be freezing or burning hot without CO2. However, CO2 is a greenhouse gas, meaning it traps energy from the sun as/heat. That makes temperatures near the ground rise. Human activities, especially the widespread burning-of fossil(化石）fuels，have been sending extra greenhouse gases into the air. This has led to a rise in average temperatures across the globe.
Studies had shown forests readily absorb CO2，but there hadn’t been much data on whether city trees grow， die and absorb CO2 at the same rate as forest trees do. So some researchers decided to find out.
To figure out how quickly trees were growing, researchers tracked their diameters (the width of their trunks) between 2005 and 2014. A tree’s diameter increases as it grows, just as a person’s waist size increases as they gain weight. About half the weight of a tree is carbon, research has shown. Most of the rest is water. Over the nine years’ tracking, the researchers found city trees absorbed four times as much carbon from the air as forest trees. However, they were twice as likely to die. So over the lifetime of each type of tree, forest trees actually absorbed more CO2.
City trees grew faster because they had less competition for light from their neighbors. In a forest，trees tend to grow close together，shading their neighbors. Street trees also benefit from higher levels of nitrogen (氮）in rainwater. Nitrogen helps plants grow. Waste gases from gas-burning cars also contain nitrogen, thus enriching city air with nitrogen. Later, rainwater may wash much of it to the ground. Some street trees may also have better access to water than trees in the country because the underground water pipes can leak.
1. What can he known about CO2 from paragraph 2?| A．It is one of the side effects of greenhouses. |
| B．It greatly accelerates the process of global warming. |
| C．It results from the widespread burning of fossil fuels. |
| D．It prevents the earth from becoming unsuitable to live on. |
| A．To know about their growth rates. |
| B．To find out how much they weigh. |
| C．To check whether they were healthy. |
| D．To assess the carbon amounts in them. |
| A．They are more likely to access growth promoters. |
| B．They can enjoy more water coming from the air. |
| C．They can enjoy more shade from neighbors. |
| D．They are better at competing for light. |
| A．How urban trees can live longer. |
| B．Why city living makes trees die young. |
| C．How trees respond to dry soil conditions. |
| D．Why faster-growing trees absorb more CO2. |
2 . With all the recent concern about the environment，people want to see their money used to better the planet. Here are four well-known environmental organizations.
World Wildlife Fund (WWF)
The World Wildlife Fund is perhaps one of the best-known organizations for the protection of endangered species and their habitats around the world. They’ve been around for over 45 years. You can donate through their website worldwildlife. org, join their organization as a member, or adopt an animal through their online adoption center.
National Geographic Society (NGS)
National Geographic Society is well-known for their magazine and their specials on TV. The organization itself is one of the longest-running in the world—they’ ve been around since 1888. focus on exploration and conservation of forests, oceans, habitats, species and societies. You chopse to donate through the website nationalgeographic.com，buy something at their online store, or order a magazine subscription.
National Wildlife Federation (NWF)
Founded officially in 1937, the National Wildlife Federation tries to protect wildlife at all costs. In fact, they believe that having the public educated is the best way to help the environment—-the more you know, the more you can protect the world we live in. Donations to the NWF can be made through their website nwf. org or through other options, like matching gifts, workplace giving, or memorial donations.
Ecology Fund, com
Set up in 1976，Ecology Fund, com is run on user clicks. Advertisers buy ad space on the site every time someone clicks. The money goes to buy endangered wilderness land to protect it from companies that would destroy it. So far, Ecology Fund, com has bought land in many areas. The best thing about this site is that you needn’t donate any money—all you have to do is click.
1. Which environmental organization has the longest history?| A．Ecology Fund. com. | B．World Wildlife Fund. |
| C．National Geographic Society. | D．National Wildlife Federation. |
| A．Knowledge. | B．Management. | C．Money. | D．Patience. |
| A．The size of networks. | B．The way of operation. |
| C．The strength of influence. | D．The degree of popularity. |
