In many situations in our life, people take different methods to make up for their carbon footprints,such as paying a bit more when buying flights with certain airlines or planting trees. But have you ever wondered what a carbon footprint is? Where does it come from and how is it measured?

Originally a footprint was the print made by a foot, just as you might imagine In the 1960s, due to the development of space travel, the word gradually changed to mean the landing area for a spacecraft.It has continued to gain popularity in the field of technology, with people talking about the footprint of computers, printers and many other such machines. Small footprints are considered to be a positive thing, while large ones are generally bad.

When the term was associated with carbon dioxide, the meaning changed again. Now, it refers to the amount of carbon dioxide you produce with any action or activity. Today, everyone in the world has a carbon footprint, and it influences the environment directly, for carbon dioxide is known to result in the greenhouse effect. Your carbon footprint is closely related to your lifestyle. Small footprints mean that you re living a simpler, healthier and more sustainable life.

But what happens if it's big? Well, there are many ways to make up for it, some of which are mentioned in the beginning. To put it more specifically, you can balance the negative effects of your actions by using green fuels, recycling, reforestation(重新造林) and a number of other activities to reduce the emission of carbon dioxide.

So, before you print out this booklet, think about your carbon footprint and make the right choice1.

We're often reminded of the importance of protecting the planet as we see it for future generations — and children at St Oswald's CE Primary School Chester certainly agree.

Nine-year-old Isohel Kelleher from the school's Hummingbirds class thinks adults need to take notes. "Sometimes they can be busy and I don't think they think they can make a difference, but if everyone does a little bit it all adds up," she tells Huff Post UK. "We started looking at plastic pollution in our oceans and the things like plastic bags that are polluting them, " she says. "Fish can eat the plastic and they can die, or we might even eat the fish ourselves. ”

Mr Timms, Isohel's teacher, has been leading a new project at the school which lets children loose creatively to raise the awareness of the need to be more environmentally friendly. The entire Hummingbirds class, which is made up of nine-year-old and ten-year-old pupils, has been busy writing poems and creating online videos to warn adults about the serious situation of our oceans and wildlife.

Mr Timms thinks children play an important role in teaching us how to take care of the things around us. "We sometimes overlook how much we can really learn from children," he says. "It is really hard to believe having parents come in saying that their children have been asking them to stop using plastic and to recycle more, and even stopping them using plastic straws. ”

Mr Timms is proud of his Hummingbirds class. "The message that they would like to send to the world is simple: stopping this isn't someone else's job, and it won't be OK if we just leave it."

Introduced species have a bad reputation. It has been believed that the species mix in a particular place should remain as unchanged as possible. But this is just an opinion. Other opinions are possible. A study published recently by Dov Sax of Brown University, thus asks how the benefits of introduced species might be better assessed, so that opinions can be more informed. Specifically, he identifies several aspects for that.

Initially, whether introduced species provide direct human advantage is taken into account. Dr. Sax and his colleagues ignored crops, since their benefits are obvious. But they included transplanted grass species that have gone wild，yet provide grazing(牧草)for domestic animals, and introduced forest trees that produce wood for construction.

Another factor is their possible benefit to the ecosystem into which the introduction has happened. Such introduction is sometimes made to reduce the risk of a localised species becoming extinct. Pyne’s ground plum(李子)，native to a handful of sites in the central basins of Tennessee but now transplanted to others, falls into this category.

The last value is experienced on an emotional rather than a practical level. Lots of people feel good about native wildlife, which is generally the main motive for its conservation. But that feel-good factor can extend to introduced species as well. Such value can cut both ways, however. For example, ring-necked parakeets, an Asian and African species, have been spreading through Britain for several decades. Some find them a colourful addition to the local wildlife, others a noisy competitor for native birds.

In light of their analysis, Dr. Sax and his team therefore suggest that researchers studying introduced species should in future create a clear distinction in their studies between changes that have happened and judgments about the value of those changes. In addition, when making those judgments, they should acknowledge all types of values, rather than focusing narrowly on one or two of them.

That done, many species will surely still be accused of possible damage. But others, badly thought of in the past, may not.