Humankind was created in the image of God, thus representing God as His stewards, to rule the natural environment in a faithful and fruitful way…. The ecological crisis is rooted in humankind’s greed and refusal to practice good and faithful stewardship within the divine boundaries of creation.

The relatively new science of chronobiology has uncovered some totally unexpected facts about living things, as Susan Perry and Jim Dawson report in their book The Secrets Our Body Clock Reveal. "Weekly rhythms -- known in chronobiology as "circaseptan rhythms" -- are one of the most puzzling and fascinating findings of chronobiology. Circaseptan literally means "about seven;" ...

"At first glance, it might seem that weekly rhythms developed in response to the seven-day week imposed by human culture thousands of years ago. However, this theory doesn't hold once you realize that plants, insects, and animals other than humans also have weekly cycles. . . . Biology, therefore, not culture, is probably at the source of our seven-day week." [14]

Campbell summarizes the findings of the world's foremost authority on rhythms and the pioneer of the science of chronobiology: "Franz Halberg proposes that body rhythms of about seven days, far from being passively driven by the social cycle of the calendar week, are innate, autonomous, and perhaps the reason why the calendar week arose in the first place." [15] ...

The most intriguing of all biological rhythms are those set to a clock of about seven days. In his chapter "The Importance of Time," Jeremy Campbell reports:

"These circaseptan, or about weekly, rhythms are one of the major surprises turned up by modern chronobiology. Fifteen years ago, few scientists would have expected that seven-day biological cycles would prove to be so widespread and so long established in the living world. They are of very ancient origin, appearing in primitive one-celled organisms, and are thought to be present even in bacteria, the simplest form of life now existing." [20] ...

One of Franz Halberg's amazing discoveries is that of an innate rhythm -- about seven days -- occurring in a giant alga ... popularly known as mermaid's wineglass (Acetabularia mediterranea). When this "primitive" alga is subjected to artificial schedules of alternating light and dark spans of varying length over many days, this single intact cell is somehow able to translate all that manipulation of light and darkness into the measurement of a seven-day week! ... Involved experimentation with rats, face flies, plants and other life have revealed circaseptan rhythms similar to that of the mermaid's wineglass. [21] ...

"A particular function of the body may have a spectrum of rhythms with a dominant frequency that is very different from the dominant frequency of the spectrum of rhythms in another function, perhaps widely separated in space. Yet no matter which frequency component is the primary one in any given function, all rhythmic systems of the body probably possess an innate circaseptan frequency so that when they cooperate to perform a specific task which is body-wide, say, an immune reaction, the reaction occurs on a weekly schedule.

"That schedule is a compromise between too much time and too little. A day and a night, which is the dominant frequency in the spectrum of many routine body chores, would not be long enough to complete the complicated array of chemical and other activities that compose the immune defense reaction, and a month would be too long." [26]

In addition to being the key coordinating rhythm for the rest of the body's many rhythmic interactions, a seven-day cycle has been found in fluctuations of blood pressure, acid content in blood, red blood cells, heartbeat, oral temperature, female breast temperature, urine chemistry and volume, the ratio between two important neurotransmitters, norepinephrine and epinephrine, and the rise and fall of several body chemicals such as the stress coping hormone, cortisol. "In fact," Perry and Dawson note,

"weekly rhythms appear easiest to detect when the body is under stress, such as when it is defending itself against a virus, bacterium, or other harmful intruder. For example, cold symptoms (which are really signs of the body defending itself against the cold virus) last about a week. Chickenpox symptoms (a high fever and small red spots) usually appear almost exactly two weeks after exposure to the illness.:" [27]

Doctors have long observed that response to malaria infection and pneumonia crisis peaked at seven days. Organ transplants face similar crises as the body's immune system attack the foreign organ.

Complete text and references:

http://www.biblestudy.org/godsrest/mysterious-seven-day-cycle-in-plants-animals-man-1.html
http://www.biblestudy.org/godsrest/mysterious-seven-day-cycle-in-plants-animals-man-2.html

What’s the point of worrying about the environment when the whole earth will be burned up soon when Jesus comes?
Two points which I found relevant as an answer to this question:

1) How do we reflect the character of God in our dealings with the environment?
This was the point emphasized by Jonathan Gallangher.
He quotes the SDA Statement on the Environment:



He says:

"At the heart of the rebellion is the spirit of selfishness—which is what evil is all about. At the heart of pollution, habitat destruction, resource exhaustion, is that same spirit of selfishness which says, 'I want this. I don’t care about the results. Me, me, me.'"

"[There is] a tremendous future for those who want to be with God and accept his forgiveness and healing. But that’s then. What about now? Does the environmentalist Christian say, 'It’s okay. In the end God will fix it. It doesn’t matter what happens now'? A thousand times no! Because the way we are now is the way we will be. If we don’t care now, we’ll never care. And what about that precious quality of life in the present? For ultimately as we damage the environment we are destroying what God made."

2) There is a connection between good stewardship of our bodies and of the ecology in which our bodies live, and this is the argument of the lesson. This is the point emphasized by David Trim and Alex Belisle in their replies to the essay about the lesson in Spectrum. They say:

"The lesson is encouraging us to take our holistic view of health to a new level (perhaps a new depth of understanding), and see that we CANNOT live healthfully in a poisoned world.... Responsible concern for the environment is not some nice extra thing we could take on. Rather, the lesson indicates, it is an essential, integral, inevitable part of our health message. We can't duck the issue unless we are also prepared to ditch our health message - which I'm sure we're not. Good stewardship of the 'earth, the sea and the springs of waters,' and protesting their contamination, is part of that message - and we ought to see it in that light."

"[By] taking better care of our planet ... [we are taking] better care of ourselves. It's very simple really. Can we waste less? Can we create less garbage? Can we help in local clean-up campaigns in our neighborhoods? How can we be better stewards?"

Speaking of which, does our burning of fossil fuels damage the environment? If so, what should we and/or can we do about it? Stop driving cars? Stop using heavy equipment on our construction jobs? Stop using public transport like planes, trains, etc.? How far should one go?

Brazil has ideal conditions for becoming a major world producer of biodiesel. It has a vast amount of arable land, part of which is not suitable for food crops but has the right soil and climate for growing a range of oilseeds.