Autumn Leaves: The science behind one of the most beautiful seasons

Hi everyone!

We know that at the time this post is being published it will still be August, and the height of summer here in the Northern Hemisphere, but within the next two months or so, autumn will well and truly be upon us. So, today, we thought we could talk a bit about the science behind this beautiful season.

Thinking of autumn automatically brings to mind images of crisp mornings, cosy evenings, and of the picturesque falling leaves with their hues of red, orange, yellow and gold. The change of colour of these leaves marks a change of seasons, and the decreasing temperature and light levels that goes along with that. But why do these leaves lose their greenness and fall from the trees?

Trees' leaves contain a chemical called chlorophyll which allows them to convert water and carbon dioxide into glucose, or sugars, through a process called photosynthesis. This is how they gain energy from sunlight. Chlorophyll is green in colour, giving the summer months, when trees photosynthesise the most, that beautiful fresh, green backdrop. However, as the light levels start to fade throughout the months of September and October, the tree receives less and less sunlight in order to gain energy from. During the summer, chlorophyll naturally breaks down and is replenished, but now this process slows down, meaning the chlorophyll isn't replaced as quickly or as much. This causes the green colour to start to disappear.

The chemicals that cause the classic orange and yellow shades associated with autumn, are actually always contained within the leaves, but are hidden by the stronger green colour produced by the chlorophyll. So, as the chlorophyll breaks down, these orange and yellow colours are revealed. Interestingly, each species of tree has slightly different colouring of leaf, giving a stunning wide array of shades. Not all species will produce red leaves, and the ones that do require specific conditions, in particular, an extremely dry and sunny year.

The next stage is 'the fall'. This is when the leaves die and drop off of the branches, allowing space for new growth in the spring. But, the trees' use for them is not over. The leaves coating the ground around the tree improve the soil's drainage and ability to retain moisture. They also host a variety of species of insects and fungi which decompose them.

The ideal conditions for this process is a long 'Indian' summer, which allows the leaves to keep producing energy for the tree through photosynthesis for as long as possible, followed by a short burst of cold temperatures which speed up the changing of colours and the fall, giving us the maximum amount of yellow and orange leaves. If we have a wet autumn, the process is slowed down, meaning many of the leaves will turn completely brown before falling off.

We hope you found this post interesting and helpful, and will see you again next week with another post,

Your Green World Blog Team💚

Sources:
https://www.kew.org/read-and-watch/why-do-leaves-change-colour
https://www.forestryengland.uk/blog/why-do-leaves-change-colour-autumn

Images:
Autumn Leaves, owned by Hideo (on flickr.com), is licensed under CC BY-NC-ND 2.0.
Autmn Beech Leaves, owned by Jonas Strömtedt (on flickr.com), is licensed under CC BY 2.0.

Comments

16.08.2020 Animal of the week: Elephant

Hello. On the 12th of August it was International Elephant Day, so we decided that this week's post should be about elephants. Elephants are the largest living land mammals. There are three types of elephant; the African bush elephant; the African forest elephant and the Asian elephant. African elephants have larger ears, whereas Asian elephants have smaller ears. Elephants use their trunks to breath, bring food and drink to their mouths and to grasp objects. Elephants' legs are like pillars. They carry the Elephant's massive weight. African bush elephants weigh 6000kg, Asian elephants weigh 4000kg and African forest elephants weigh 2700kg. Basically, they are very heavy.Elephants eat grasses, small plants, bushes, fruit, twigs, tree bark, and roots. Elephants can live up to 70 years old in the wild. They communicate by sight, touch and smell. Sadly, these wonderful mammals are in danger. African elephants are listed as vulne...

The limits of the Earth - the planetary boundary model

Hi everyone, So today we're talking about a model that was introduced in 2009 and has offered a new perspective to thinking about environmental issues. The planetary boundary model has 9 boundaries, each has a safe zone. Once the safe zone is exceeded, the stable conditions on our planet are considered at risk, and there can be severe and possibly irreversible changes. The nine boundaries are considered separate however, they greatly affect each other. Novel Entities describes the introduction and accumulation of man-made novel chemical compounds. These include pesticides, nuclear waste and microplastics. Stratospheric Ozone Depletion refers to the depletion of the ozone layer which was a major problem in the 90s. Atmospheric Aerosol Loading is air particle pollution. Ocean Acidification is self-explanatory. The boundary Biochemical Flows is composed of two separate boundaries; nitrogen and phosphorus. Both of the ele...

Greta Thunberg's Speech at the UN Climate Action Summit 2019

Hi Everyone! I thought I would share the transcript of Greta Thunberg's inspiring speech from the UN Climate Action Summit. The phrase we remember is 'How dare you!'. But what did she really want us to take away from it? She wanted us to act, so watch the video using the link below and take action because the world isn't just going to heal itself. Greta Thunberg's speech at the UN Climate Action Summit video "My message is that we'll be watching you. This is all wrong. I shouldn't be up here. I should be back in school on the other side of the ocean. Yet you all come to us young people for hope. How dare you! You have stolen my dreams and my childhood with your empty words. And yet I'm one of the lucky ones. People are suffering. People are dying. Entire ecosystems are collapsing. We are in the beginning of a mass extinction, and all you can talk about is money and fairy tales of eternal economic g...

19.07.2020: Animal of the week: Honey Bees

Hi everyone, This week's animal is the honey bee. Enjoy! General Information An average honeybee hive is made up of one queen, hundreds of male drones and thousands of female workers. If the queen bee dies then a new queen is created. The workers select a young larva and feed it with a special food called ‘royal jelly’. The ‘royal jelly’ makes the larva grow into a fertile queen. Queens live for several years but the workers only live for five or six weeks. An average worker will make a twelfth of a tee spoon of honey during her entire life. Drones are turned out of the hive and left to die in Autumn. In the summer months, the queen bee is very busy, she can lay up to 2500 eggs in a single day. How they affect the world around them Honey bees are very important for flowers, fruit and vegetables. This comes from the fact that they are pollinators. They help the plants by transferring pollen between male and female parts, meaning the plants can g...

Linking climate change and inequality - 'The Great Carbon Divide'

Hey everyone, Have you heard of 'The great carbon divide‘? It is often referred to as the 'carbon footprint gap' or the 'emissions imbalance‘, and produces frightening numbers. The great carbon divide describes the huge gap between the amount of carbon dioxide the rich versus the poor emit, and these numbers shocked even us. What does this mean? There have been many different studies, and all of them show terrifying results. One study from the Guardian and Oxfam, reports that the richest 1% of the world's population emit more carbon than the poorest 66%. The richest 1% consist of 77 million people, which may seem like a lot at first, but the poorest 66% refers to over 5 billion people! Africa, which is home to 17% of the world's population, only causes 4% of the world's emissions. This top 1% emitted 16% of global CO2 emissions in 2019, that's 5.9 billion tonnes of CO2. Modelling suggests that it would take someone who isn't in the top 1% about 150...

The Climate Book by Greta Thunberg | review & thoughts

Hi Everyone! You may be aware that Wednesday was International Women's Day, so today I wanted to share a book review for a book written by one of the most inspiring women of our generation: Greta Thunberg. She is, of course, the legendary creator of the Fridays For Future movement and has inspired thousands of children to skip school on Fridays to protest for the climate. She recently compiled a book, simply entitled: The Climate Book. Here are my thoughts. This is a compilation of articles and essays from the best climate scientists, activists and high-profile people, which makes up, in my opinion, the climate bible . It quite literally encompasses everything you may want to know about the climate crisis, from the science, to how it affects us, what we've done and have yet to do, and so much more. This book is everything. I have not yet read the whole thing, because let me tell you, this book is HUGE. It's also of course very den...

Photosynthesis: what is it and how is it linked to climate change?

Hi Everyone! Welcome to another post, this time about photosynthesis! This is an extremely important process that I've learnt a lot about in school and lots of you may know about it but this will hopefully refresh your memory! What is it? Photosynthesis is a natural process that takes place in a leaf. It turns carbon dioxide into oxygen, which is so important for climate change, but more on that later! This enables the leaf to get energy. The equation is as follows: Carbon Dioxide + Water ~> Glucose + Oxygen CO₂ + H ₂O ~> C ₆H₁₂O₆ + O₂ It's hard to write it on here but to make the glucose and oxygen you need sunlight and chlorophyll. How does it happen? To understand this, you need to know a little about the structure of the cross-section of a leaf. Just type 'cross section of ...

10 Animals on the edge of extinction - you did not know about No.2

The Kākāpō ~ New Zealand's green teddy bear-parrot The Kakapo is a bird mainly found in New Zealand. It is a rather curious creature, a pretty big, green, nocturnal parrot that cannot fly and looks like a mixture of a parrot, a penguin, an owl and a teddy bear. Kakapos are on the verge of extinction due to their peculiar breeding habits, predators, and hunters. They are flightless and nocturnal and are the biggest parrots in the world. They can also live for up to 120 years! History Like most living creatures, the number of Kakapos in New Zealand was healthy before humans arrived. They waddled across the islands like nothing else. However, when people came to New Zealand, they started hunting the Kakapo for its feathers, meat and skin. They also brought alien species such as rats, weasels or cats that posed a threat to which they were not accustomed to. Their survival "trick" (not really a new thing, maybe the Kakapos like it old-fashio...

Green Pets || easy house plants to get you started // best house plants for beginners

Hi Everyone! Today I wanted to talk to you about some easy house plants you could look after to get you started on your green pets journey. These are plants that are easy to look after and that I recommend for an introduction into caring for house plants. If you are a beginner or want to look after some plants, then this is the post for you! 1. Cacti - moon cactus I don't actually have a cactus, but they are the obvious place to start. They need little water and thrive in warm conditions; they are described as "low maintenance". I have done some research and it looks like the moon cactus (Gymnocalycium mihanovichii) is the best one in terms of not being too fussy with needing minimal water and tolerates lower light levels. I would like a cactus at some point, but if you are just starting out wanting to care for some house plants, then this is the one to start with! 2. Aloe Vera One of my first house plants, this is one that is rela...

Major ocean currents and how they affect global temperatures

Hi everyone, This week we're talking about ocean currents. Ocean currents are part of the ocean's circulation system and influence local and global weather patterns. They are produced by gravity, differences in water density, winds on the ocean surface and Earth's rotation on its own axis. They cause the movements and exchanges of different ocean properties such as salinity, temperature and nutrients. Ocean currents can flow at speeds of up to 4m per second however most flow at speeds between 5cm and 50cm per second. Weather patterns and ocean currents constantly influence one another. Ocean currents follow similar paths as global wind do, transferring heat from the equator to polar regions. They create and influence ecosystems worldwide, especially marine ones. However they also spread plastics and microplastics around the world far from their original source. This system of ocean currents is often referred to as a global conveyor belt. Today w...

Green World

Search This Blog