Natural resources on Cape Cod, Martha’s Vineyard, and Nantucket are under intense pressure. Problems such as climate change, fisheries collapse, ozone depletion, and biodiversity loss have proven that this holds true worldwide. You can have a positive impact on your immediate surroundings, global environments, and future generations. The most important thing to do is to think before you act and, increasingly, before you buy.

Here are some issues and questions to keep in mind when you are planning a green project or purchase - or making a lifestyle decision:

• Sources: Is it produced locally? If not, where does it come from, and how does it get here?
• Ingredients: What is it made from? How is it grown, extracted, or manufactured?
• Costs: Is it a smart buy when considered on a life-cycle basis and from economic, environmental, and social perspectives?
• Desires: Is it a want or a need?

Here are some specifics to ponder:

Location is very important. Products sourced locally - either grown, found, or made on the Cape, Vineyard, or Nantucket - are generally more resource efficient. They offer lower embodied energy because they haven’t been transported a long distance. Fresh, organic produce when in season, local seafood harvested sustainably, and cranberries grown organically are obvious examples.

Patronizing locally owned businesses is also important. When money spent here stays here, it cycles through and supports a sustainable year-round economy.

Products of natural origin are best. Things derived from plants grown sustainably or animals treated humanely are ecologically sound in use, and they decompose naturally. In the building trades, products made using materials harvested on a 10-year cycle or less are a good idea, with examples including bamboo and cork flooring, cotton batt insulation, linoleum, seed board, wheatgrass cabinetry, and straw bale walls. In fabrics, cotton, wool, hemp, and other natural materials represent the best choices. Naturally occurring inorganic materials such as stone can be fine, so long as they are extracted in a low-intensity manner and not shipped long distances.

Products containing synthetic chemicals and materials - including petroleum-derived plastics, fertilizers, and pesticides - offer higher embodied energy due to their industrial origin. They may release harmful volatile organic compounds in indoor environments, and they may contaminate outdoor environments. They also may be difficult or impossible to recycle.

Reduce, reuse, and recycle is more than a mantra. Not consuming anything is a surefire approach to minimize environmental impacts, albeit an impractical one. Purchasing less stuff, buying things that aren’t overpackaged, and downsizing a vehicle or house represent resource-efficient solutions. The same may be said for using things more than once, for purchasing previously owned products and materials, for buying things that can be reused or recycled, for practicing recycling, and for buying recycled goods.

In truth, neither paper nor plastic is the right choice, even if a bag contains recycled content or is recyclable itself. The greenest option is no bag at all - or a reusable bag made of cotton or other organic materials. Why? Recycling paper and plastic reduces the use of virgin materials, but it typically involves energy-intensive transport and manufacturing activities.

Life-cycle costs and true costs are critical. Purchasing decisions have multiple cost dimensions. Considering only the sticker price, the capital cost, or the construction cost is often an unwise decision. Accounting for life-cycle costs is a smarter approach. Why? Appliances, vehicles, buildings, and many other types of purchases operate on energy, water, and other resources. Typically, things with a lower initial cost are less resource-efficient, which means that they cost more to use and operate throughout their lifetime. It can make sense - and save dollar and cents - to spend more up front because efficiency pays off in the long run.

The greenest decisions also factor in true costs - the economic, environmental, and social impacts not reflected in prices. Why? The prices of fossil fuels would be higher if they accounted for military activities in the Mideast and elsewhere, air and water pollution, mercury contamination in fish, and the adverse effects of climate change. Synthetic fertilizers and pesticides, foodstuffs grown and produced at industrial scale elsewhere and shipped here, and many other commodities would be more expensive if prices told the ecological truth. And efficient, renewable, organic, and local products would represent even better deals than they already are.

Wants and needs are distinct. The United States uses far more than its share of the world’s resources and produces more greenhouse gases than any other nation for one primary reason: We are rampant consumers. Houses are mushrooming in size. “Uber-vehicles” are prowling the roadways. Consumer electronics devices are proliferating. Pressure to remain on the cutting edge and to “keep up with the Joneses” is intense. It doesn’t have to be this way: Green thinking doesn’t require sacrifice, but it can involve downsizing, rightsizing, and naysaying.