When land is cleared, habitats are lost. It may be cleared for agriculture. It may also be used for building new homes or businesses. Within the past 100 years, the amount of land used for agriculture has almost doubled. Land used for grazing cattle has more than doubled. Many wetlands have also been lost to agriculture. The U.S. has lost almost all the natural tall-grass prairies. Thee areas of tall thick grass have virtually disappeared. These areas of land had thick fertile soil. Their grasses had very deep root systems. These deep and thick roots reduced the amount of soil erosion. They also were home to many plants and animals. Prairies were wonderful places. They were home to colorful flowers, prairie dogs, and herds of bison.

Why may land be cleared?

Patricia Cross and her boyfriend Larry Osborne , two students in a San Francisco school , become expelled for the publication of an off-campus underground paper . As a result , a philosophy professor , Dr. Jonathon Barnett , resigns his teaching position and decides to become an advocate for the counterculture youth movement and , specifically , the use of LSD . The hippies of the Haight-Ashbury district first see him as a hero and then as something even more . Dr. Barnett even makes an appearance on the Joe Pyne TV show to voice his support of the hippie community and the use of LSD . One scheming young man sees the opportunity to build Dr. Barnett as the head of a cult centered around the use of LSD . He hopes to earn profit from the users , Dr. Barnett's speeches known as '' happenings , '' and their lifestyles . At a massive LSD-fueled dance , Patricia begins to have a bad trip Which leads to an argument between her and Pat , ultimately splitting the couple up . After Patricia realizes that she's pregnant , Dr. Barnett advises her to have an abortion , ultimately leading to Patricia attempting suicide . However , Larry saves her and makes the destruction of Dr. Barnett's cult his primary objective . Larry shoots Dr. Barnett from the crowd at one of his massive speeches . As another hippie in attendance calms the audience and Elliot sees his new leader for their cult-like organization , Larry realizes that his assassination of Dr. Barnett simply made him a martyr for the hippie movement .

What Haight-Ashbury group supported the professor, a group he celebrates in return on the Joe Pyne Show.

After his cousin Joe dies , Layne Vassimer and his girlfriend Macy , along with their friends Stephen , Maurice , Iris and Katrina , decide to clean up Joe's house with the intention of selling it . When they see it for the first time , they discover the house completely covered in plates of iron armor . The group also finds crop circles in the nearby cornfield . When Iris , one of their friends , suddenly disappears they realize something is really wrong . During a blackout , the house is attacked by aliens , who had previously killed Joe and abducted Iris . The group figures out the aliens are allergic to iron , Joe had covered the house in it to keep them out . They attempt to fight the aliens off , but the house is eventually blown up with Layne , Macy , and Katrina the only survivors . In the end , they drive off , listening to the radio . They hear a news report stating that the blackout they experienced affects five western states and parts of Canada . They also hear that people everywhere are being attacked by '' strange creatures . ''
Who killed Joe and why do Layne Vassimer, Macy and their other friends clean up his house?