In the 33 years since the first Earth Day was celebrated in the United States, our thinking has about it evolved from focusing on one day to considering "Earth Day, Every Day." Still, singling out calendar day helps raise awareness about the environment, and compels us to think about how daily habits and practices contribute negatively—and positively—to the state of our planet. Today's column focuses on the environment, from polluted sites to scenes of exquisite beauty.

"There is a lot more trash out there than I expected." This was the observation of a marine pollution researcher after his first flights over the Eastern Garbage Patch, an area of the Pacific Ocean where currents converge to create a floating landfill the size of Alaska. The vivid images, clear descriptions, videos, and animated diagrams in the iBook edition of Loree Griffin Burns’sTracking Trash: Flotsam, Jetsam, and the Science of Ocean Motion ($9.99; Gr 4-9) will no doubt bring readers to the same realization. The title, one in the “Scientists in the Field” series (HMH, 2007) follows the efforts of Curt Ebbesmeyer and other scientists whose work studying ocean currents included tracking the routes of “roughly 80,000 sneakers" and 28,800 plastic tub toys adrift in the Pacific Ocean after two (separate) cargo spills, and referred to as “the largest and (cheapest) ocean drift experiment ever undertaken.”

The ebook has been enhanced with age-appropriate video content—one or two short multimedia components per chapter, including a National Oceanic and Atmospheric Administration (NOAA) animation of ocean currents that is both soothing and dizzying at the same time. The news is not all bad, though—readers also learn about scientists and conservationists who use techniques as basic as beachcombing and as advanced as satellite tracking to identify and clean up our oceans.

Tracking Trash inspires further research and individual commitment to the environment, and with links to relevant websites and ongoing projects accessible from the tablet, the creators of the app have made it easy for students pursue their interests. Bonus: unlike the print version, the ebook edition isn't made out of a tree and won't end up in a landfill.—Paula Willey, Pink Me 

BBC Earth Wonders (BBC Worldwide LTD, $3.99; Gr 2 Up) for iOS offers a collection of images and videos showcasing the fierce and fascinating beauty of our natural world, including rare animals, plants, and natural phenomena. As such, it supports science research, though the brevity of the text may make it a supplemental resource, unless, of course, it’s visuals your students are seeking. The app’s real stand-outs are the hundreds of high-quality images and numerous videos that bring information to life in a way that text cannot. These can be accessed alphabetically, or by theme, or by tapping a globe. Providing glimpses into the incredible and often dangerous facets of nature, the videos are sometimes grisly; sensitive viewers may be disturbed by a pack of lions hunting and devouring an elephant. Then again, what child can resist seeing a Venus fly trap capture its prey? Other videos are sheer awe and beauty, such as the time-lapse scenes of the aurora borealis. Users may be put off by the somewhat clumsy interface and the prominent link to purchase the BBC’s Planet Earth television series after each video, but kids will love navigating via the spinning globe. Overall, a welcome resource for those with a keen eye for nature.—Allison Tran, Mission Viejo Library, CA
The following are excerpts from apps reviewed earlier in this column—all essential purchases. For the full reviews, follow the title links.

Screen shot from Our Choice (Push Pop Press), Gore.

In Our Choice (Rodale, 2009), Al Gore placed the response to global warming squarely in the world’s collective hands, as he detailed the wide-ranging crisis and identified possible solutions. With the publication Our Choice in app format (Push Pop Press; $4.99; Gr 9 Up; trailer) Gore’s message is delivered via a not-to-be-missed, multimedia, e-reading experience. An earnest video introduction by the author is followed by a cleverly composed tutorial, also narrated by Gore, on how to manipulate the app and its contents. As in the print edition, topics include solar and wind power, geothermal energy, biofuels, carbon capture, nuclear power, population growth, politics, and more. The text has been edited for conciseness, and information has been updated; for example, the recent nuclear meltdown in Japan is addressed. Spectacular pop-out, captioned photos in full color, including some with additional voice narration; compelling video clips, both current and archival; and interactive “infographics,” all unquestionably high in wow appeal, are included. While best suited for the high school audience, teachers may want to select some of this impressive content to share with their middle school students.—Alicia Eames, formerly with NYC Public Schools Fascinating before-and-after images of a range of environmental phenomena are presented in Fragile Earth (HarperCollins/Aimer Media; $2.99; Gr 6 Up), a photo gallery detailing “Man’s Impact” on the environment, “Deserts and Droughts,” “Warming World,” “Water Power,” “Wild Weather,” and “Natural Phenomena.” Users can filter results by date, region of the world, or theme. The paired images are superimposed over each other so it appears viewers are looking at time-lapse photography; by sliding the photos right or left, they can choose to view them side-by-side, or one at a time, full screen. Pinching and stretching provides detailed close-up views. Textual information, which is accessed via an information screen, partially obscures the related image. Some of the before-and-after photos span short time periods; pictures taken of the same street before and during a dust storm in Kansas in 1935 are separated by 15 minutes, while others allow viewers to see changes such as those visible in the satellite photos of Amazon deforestation over a nine-year period. The aftereffects of tsunamis and earthquakes and other natural events make clear how powerful—and devastating—those forces can be. This is a great visual resource for students or teachers working on environmental projects or lessons, and one that will work well for the flipped classroom.—Sydnye Cohen, Brookfield High School, Brookfield, CT Eds. note: Since our review of Fragile Earth was published, the app has been updated with 12 new sets of images including those of the devastation caused by Hurricane Sandy; urban expansion, Tehran, Iran; melting ice in Hudson Bay, Canada; and the impact of the 2011 earthquake that hit Christchurch, New Zealand. Acknowledging that the world’s population reached seven billion during 2011, National Geographic Magazine launched a year-long editorial series focusing on population. The app, 7 Billion: How Your World Will Change ($4.99; Gr 7 Up), is a companion to that series and it’s stunning collection of photographs, eye-opening charts, and insightful articles and videos paints a broad picture of the impact of population growth on the planet. Including essays tackling such topics as the acidic effect of pollution on ocean creatures and sea levels, the desperate need to preserve heirloom seeds to feed growing populations, and the work of strong-willed women who are changing the face of family planning in developed countries, this app is all that readers have come to expect from National Geographic, and more. An introductory video highlights the realities of 7 billion people on the planet. Interactive statistical maps include “The Shape of Seven Billion,” which presents growth and consumption by country in relation to the impact on resources. “Where and how we live” relates issues of life expectancy, sanitation, education, fertility, technology use, and carbon emissions to income levels, while “The Infant Formula” illustrates that as prosperity grows, birth rates decline. Numerous other colorful and informative graphics are also offered. This thought-provoking title will have wide value and use in an educational setting, specifically for secondary students in statistics, civics, and environmental science courses. Students studying social justice issues and population growth will also benefit from the information in this rich resource.—Danielle Farinacci, Sacred Heart Cathedral Preparatory, San Francisco, CA