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

Heatwaves - what's so bad about them?

Hi everyone, Today we’re talking about heatwaves and what effects they have on us and the environment. Heatwaves are becoming ever more common, with 2023 breaking multiple world records. In China, 52.2°C were recorded at one point and the coastal waters near Florida, USA, were as warm as a hot tub. This is because of the combination of climate change and El Niño , both of which make the effects of the other worse. But we can’t push the blame onto El Niño. When analysed it became clear that without human made climate change the USA heat records would have been almost impossible. So what exactly are the effects of such high temperatures. A study in Europe found that the 2022 heatwave possibly caused over 70 000 heat related deaths. Although it is sometimes hard to tell whether or not someone died from the heat or from something else, after analysing the data the team found that their original estimate of 62 000 people (which is still a lot) was probably ...

December Top Tips | 10 ways to re-purpose a plastic bottle

Welcome to December! We thought it would be cool to find 10 ways you can use a plastic bottle even after you have refilled it gazillion times, so you don't waste all the plastic . Because, even if you try to avoid plastic bottles at all costs, you will inevitably end up using hundreds of them throughout your life. The impact on the environment is undisputed, from the land animals to the creatures of our seas, plastic bottles can have a detrimental impact. But we can reuse them in lots of fun ways, here are our ten favourites. Have a good December and a great new year, you'll hear from us! 1. Bird Feeder At one of our blog meet-ups, we actually made a bird feeder out of an old plastic bottle, so this is definitely one we can vouch for. It's super simple, as long as you have some good scissors to cut the bottle and a suitable place to hang it. Below is a photograph of ours for some inspiration, and there are plenty of resources online to ...

100 amazing animal facts | 100th post special

Hi! This is our 100th post and to celebrate, we have decided to present you with 100 absolutely random facts about animals. Enjoy! The loudest animal in the world is a 2cm long prawn, the pistol shrimp. Hummingbirds are the only birds that are known to fly backwards. One bite from the world's most powerful snake can kill 100 people, the inland taipan. Mosquitoes kill 725 000 people a year making them the most dangerous animals in the world. The mayfly has the shortest known lifespan in the world, only 24 hours. The horned lizard can shot blood from its own eyes. Koalas can sleep for 22 hours a day. Swifts can fly for almost an entire year without landing. Garden snails have 14 000 teeth. The tongue of the blue whale weighs as much as a car. ...

Wildfires

Welcome back to Green World, In the last few months, wildfires have been raging across the globe. Hawaii, Canada, the USA, Spain, Portugal, Italy, Greece, Tunisia and countless more have been affected. But what are the environmental impacts of such a blaze? The USA has had an average of over 70 000 wildfires a year since 2000. In 2020, Californian wildfires emitted more than 90 million metric tons of carbon dioxide, which is more than the state's power industry emits per year. It is estimated that humans start 87% of wildfires. Around the world, 4 million squ. km are hit by wildfires every single year. This emits vast amounts of carbon dioxide, which fuels climate change . The smoke causes air pollution in the entire surrounding area and can lead to respiratory problems in humans. The air pollution also kills birds, including those migrating through the area. Studies also show that socially vulnerable populations are more at risk of harm...

Coral reefs

Hello! We would love to introduce you to the topic of coral reefs and especially coral reef bleaching, as it is a greatly ignored but certainly significant topic. Have fun! 5 coral reef facts 1. The Great Barrier Reef is the largest living structure on the planet and is 2300 km long! 2. Less than 0.1% of the world's ocean surface is covered in coral reefs. 3. At least 25% of all marine animals live there. 4. Coral reefs are often known as the rainforests of the ocean. 5. In 1 square kilometre of coral reef, up to 35 tons of fish can be 'produced'. The 5 biggest coral reefs in the world 1. Great Barrier Reef (near Australia) 2. Red Sea Coral Reef (near Egypt, Israel and Djibouti) 3. New Caledonia Reef (Pacific Ocean near New Caledonia) 4. The Mesoamerican Barrier Reef (near Mexico, Belize, Guatemala and Honduras) 5. Florida Reef (Atlantic Ocean/Gulf of Mexico near Florida) What is coral? Coral is actually made up of small anim...

Energy comparison: solar (PV) panels

Hi everyone, Today I'm looking into the first on a long list of energy sources: solar (PV) panels. Are they actually sustainable and could they become our main energy source in the near future? After all, enough energy from the sun reaches the earth in 90 minutes to cover the entire world's energy consumption for a whole year! How they work There are a couple of ways to transform energy from the sun into electricity. The one we are looking at today is solar panels also known as solar photovoltaic technology. Photovoltaic (PV) technology is the key to solar panels. A solar panel is made of many PV cells. A single PV cell will produce 1-2 watts of power. They are very thin and are normally protected by glass and/or plastics. This is the best explanation I could find (click here for the source): When the semiconductor is exposed to light, it absorbs the light’s energy and transfers it to negatively charged particles in the material calle...

18.10.20 Animal Of The Week: Sloth

Hello, Sorry this didn't come out on Sunday as planned but this week's animal of the week is the sloth because the twentieth of October is Sloth Day. Habitat The sloth resides in Central and South America. It lives in the rainforests there and occasionally drops into the water for a bathe as, believe it or not, they are actually excellent swimmers! Diet Sloths eat leaves, twigs and buds which they find in the rainforest. As they don't have incisors they smack their lips together to make leaves more digestible. Sloths can survive on relatively little food as it takes a while for them to digest it. Sleep and Speed When you think of a sloth, you probably think of this slow, sleepy creature. They actually sleep for about 15 hours a day! Sloths have an extremely low metabolic rate (what basic calories your body needs to survive), which means they move at a slow pace through the trees. On average, sloths travel 40 yards per day ...

Announcement: Factfile

This image is owned by a blog editor.

February 2021 Factfile - a bit of news from the last month and more!

Hi Everyone! Welcome to February's factfile! We are very sorry that we have not posted very much so far in 2021 but we are going to hopefully make up for it in the spring. News: Source- BBC Newsround The great yellow bumblebee has been spotted in Scotland! They used to be common in the UK but their population declined by about 80% in the last century. The find is a spark of hope as it is currently endangered. This is thought to be because of a decline in natural flower meadows and a boost in farming. The team of conservationists that found it were thrilled and when we heard about it we wanted to share it with you in case you hadn't heard! Source- Guardian In the 1840s a bird was caught in the East Indies. It had never been seen before and Charles Lucien Bonaparte (Napoleon's nephew) named it the black-browed babbler. The species wasn't seen again, so the only proof that it had ever existed was a stuffed specimen. ...

23.08.2020 Animal of the week: Little Egret

Hi everyone, This week's animal is the Little Egret. This is a less well-known bird, so we are excited to share it with you! Habitat Little Egrets are a species of small heron and live in many different places across the world such as Africa, Australia, southern Asia, Europe and the UK. Like herons, Little Egrets live in open spaces that have a lake or river running through them. Some of the ones that live in Europe migrate to Africa. Diet Because it is an aquatic bird, the Little Egret feeds on a range of fish, amphibians, small reptiles and birds, insects and worms. They aren't fussy! Some Little Egrets have made use of humans and have been known to throw bread into the water to attract fish for it to eat. Dangers Little Egrets are classed as Least Concern , so their numbers aren't declining like many other amazing birds are at the moment. That's all for this week, we hope you have learnt some new facts! Images: 1...

Green World

Search This Blog