They don’t fall of their own accord, they’re evicted
Function
Leaves serve as solar collectors for a tree, gathering carbon dioxide and water from the atmosphere to create energy—sugar—through photosynthesis. In the process, they release oxygen into the air.
For a tree to stand tall and survive the ravages of wind, rain, snow and ice in winter, it has to jettison its leaves. It knows to do this when daylight gets shorter due to the direction of the Earth’s tilt relative to the sun. At that time, a chemical change takes place in the cells between the leaf and the stem. Acting like scissors, a hormone makes a cut that allows the wind and gravity to have their way with the leaf.
From the tree’s perspective, letting go of leaves is a survival mechanism. Through the summer months, it collected an enormous amount of water for the trunk and branches. Were it to freeze and expand, that would severely damage the tree. Also, the weight of snow and ice on a leaf-covered tree could bring it down or break branches that are necessary to produce leaves in the spring. Without leaves, a deciduous tree would die. So like bears, trees go dormant through the winter months.
From the perspective of the leaves, their purpose has been served. And their contribution continues as they decompose and renew the soil—from which a new plant or tree will grow. It’s the cycle of life.
Color
Leaves are green because their primary pigment, chlorophyll, absorbs red and blue light from the sun, letting the green light to be reflected. Chlorophyll is what converts sunlight into energy for the tree, so through the summer months, it’s constantly renewed in the leaves.
As the temperature drops, trees pull nitrogen from the chlorophyll and the green in leaves begins to fade. But it’s the change in the amount of sunlight that affects the change in color. With these changes, carbohydrates are transferred from the leaf to the branch and no more nutrients are brought in. With the leaves cut off from contact with the tree, the remaining sugar in the leaves’ veins promotes the formation of anthocyanin, a pigment that creates reddish colors.
According to ZME Science, different trees have different proportions of pigments. The amount of chlorophyll left in a leaf and the proportion of other pigments in it determine its color. A combination of anthocyanin and chlorophyll makes a brown color, while anthocyanins plus carotenoids create orange leaves.
Low temperatures above the freezing point help to produce anthocyanin, which produces a bright red color.
An early frost weakens the color by destroying the creation of anthocyanins, however… Where just a few tree species dominate, like in New England and Northeast Asia, color displays are intense but short. Diverse forests mean a longer display. Cloudy and warm Falls like those in Europe cause dull colors. When the leaves die and the chloroplasts are completely broken down, leaves turn a boring brown.
A Human Parallel
Change in the natural world is constant and cyclical. Everything, living and nonliving alike experiences cycles of change. As with trees, in each season there’s a time to grow and express, and a time to rest and reflect.
To everything, there is a season, and a time to every purpose under heaven; a time to be born, and a time to die; a time to plant, and a time to uproot…
In The Adult Years: Mastering the Art of Self-Renewal, philosopher and educator, Fredrick M. Hudson advised that a world in apparent chaos “requires a perspective that can find meaning in disturbing times as well as blissful times.” Indeed. The perspective he advises is a cyclical view of adult life, which he portrays as “A complex, pluralistic, multivariate flow, with ongoing cycles in nature, societies, and people.” Basically, it assumes that life ‘develops’ through cycles of change and continuity rather than in progressive, linear, straight lines, concentrates on what lasts and what changes, honors both ups and downs and acknowledges human systems as flexible and resilient requiring continuous learning and adaptation. Relating this to our topic, a cyclic view of life requires us to, like leaves on a tree, shed “unworkable habits and learn new ways to live effectively.”
For us to stand tall and survive the ravages of personal, social, political and environmental change, there comes a time when we need to jettison old paradigm thinking and behaviors, those that no longer serve us or society. This includes such things as humans being born into sin; being put here to subdue the Earth; exacting an eye for an eye; competing to separate winners and losers and believing that boundaries, borders and divisions produce security.
I appreciate the seasons—Dr. Hudson speaks of them as “chapters” in each life’s story—where nature warns us ahead of time about changes on the horizon. For one thing, they provide us the opportunity to reflect and recreate our lives in the coming new context, in part by casting off beliefs and perspectives that no longer work. And I appreciate that the process of crisis and transformation happens for the whole of humanity, as well as for individuals and nations. It’s how life evolves.
The temptation may be to hold onto our “leaves” longer, as many of our neighbors do. But ultimately, in the big picture—the cosmic forest—there’s at least one rule that never changes: “To thine own self be true. “
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