Category Archives: Landscape ecology

Why is shifting cultivation being blamed for land degradation? 

I’m on a study tour through South India, visiting different National Parks and scientific institutes. Today was my first day, and already, the lectures we had were extremely interesting…

One of the lectures I really found fascinating was given by Amit Jose Kurian, a research scholar at the Ashoka Trust for Research in Ecology and Environment (ATREE). It was about shifting cultivation, also called slash-and-burn cultivation or jhum cultivation. The question he intrigued us with was this- 

Does shifting cultivation really lead to land degradation or is that a misconception? 


A simple Google search gives us this definition for this form of agriculture- 

Shifting cultivation is a form of agriculture in which plots of land are cultivated temporarily, then abandoned so that the land can revert to it’s natural state, while the farmer moves on to the next piece of land.

Patches of cultivated land and fallows.

The farmer then returns to this land (called fallow) after a few years to repeat the process. In this way, he goes round and round an area of land reusing and managing different patches of land. 


The time taken for a farmer to return to a plot of land to recultivate it, is called fallow length. Ideally, this should be about a few years. Every plot of land is cultivated for about two years (or two harvests), before moving on. And then, the farmer returns to the this plot after 4-5 years. During this time, the forest in this plot regrows and renourishes the soil.

Recently, reports have indicated that the fallow length has been decreasing, and the plots of forest land are being increasingly cultivated and much higher frequencies. Why is that so? Is it just because of increasing demands from population growth or is there another reason behind it? 


The British were very surprised to see this form of agriculture being practiced, and called it primitive and unsustainable. Since then, the disadvantages of shifting cultivation has been widely publicized. The shortening of fallow lengths has been accused of decreasing productivity of the land and ultimately, the land becomes infertile.


The British solution to this was the lucrative plantations of timber species, and other trees that are widely used for a variety of purposes. They argued that this would maintain the forest cover, as well as provide livelihoods for the people using shifting cultivation. 


But shifting cultivation has not stopped. Instead, shifting cultivation as well as plantations are being practiced side by side. 

The problem with this is that plantations take up years to produce a harvest. Meanwhile, the land on which the plantations are planted are out of the usable area of land. It cannot be circulated back. This leaves very little land left to practice agriculture in. THAT is why, fallow lengths have been decreasing. And this could ultimately be the reason for the decreasing productivity in the plot lands and the fast decline of forests and regrowths. 

So, the “advanced” form of agriculture turned out to be a huge reason for the disadvantages of shifting cultivation. If not for this alternative, may be the fallow length would be around a decade, allowing for a better, more sustainable use of resources. 
All images from Google Images. 


The connection between living and non-living: A look at dams in floodplains

Every ecosystem, at the end of the day, is governed by the environmental factors that exist there. This, I’ve mentioned time and again. How intricate is this relationship? Take a look!


One single dam can alter the geomorphic (or landscape or environmental) factors of the entire floodplain. These changes are immediately seen in the ecology of the area, eventually leading to endemism or even extinction of the indigenous species!

A short post, but a significant one.

A happy new year! I’ve started posting late this year, but I’m as driven as ever before! Stay tuned for regular environmental updates 🙂 

Positive feedback loops: Controlling global climate

(This is the fifth post in the “feedback loops” series.)

Climate is weather, over a long period of time. Unlike weather, climate is predictable. It has a number of factors like solar insolation, rainfall, temperature and latitude/altitude that controls it in a particular place. Also, climate encompasses a large area.

Because of the spatial and temporal extent of climate, and because of the large scale environmental factors that control it, you would not expect it to change much. Global climate, in fact, does regulate itself in the short period of a few years or decades. You will be hard-pressed to find massive climate shifts in this time period in the geological record. Climate changes are usually seen in the form of cycles; the cycle have a time period of 20,000-40,000 years. It also has smaller cycles, in the range of a few centuries as well.

These cycles are generally positive feedback cycles, with a specific threshold at each end. When that threshold is breached, the environmental factors generally change in a way that allows the cycle to reverse itself. In this, I’m going to explain this phenomenon by taking the example of glacier growth and glacier melting.

Continue reading Positive feedback loops: Controlling global climate

Disturbance: Driving changes in the universe

(This is the fourth post in the “feedback loops” series)

Imagine a world where nothing interacted with anything. Each entity, molecule and atom remained in isolation. They could not feel or touch each other, directly or indirectly…….

That would be a dead world. 

Continue reading Disturbance: Driving changes in the universe

Positive feedback loops: Creating more of what’s already there!

(This is the third post in the “feedback loops” series)

Ever used a bad eraser in your life? One that has been used so much that it’s become completely black? 

What happens when you erase something with that eraser?

Instead of cleanly removing everything you have written on the page, it just makes your page more and more dirty! The harder you rub the eraser, the dirtier it gets!

This, my friends, is a small and significant example of a positive feedback loop.

Continue reading Positive feedback loops: Creating more of what’s already there!

Ecotones and edges: Explaining abrupt changes in ecosystems

Have you ever wondered why floodplains host such a variety of life? Why fishes tend to congregate in estuaries for spawning? Why humans have thrived for so long along floodplains? 

In nature ecosystems transition from one to another gradually as well as abruptly. I have gone into detail about the gradual transition of ecosystems in Across a gradient: How changing environment dictates community composition. Similarly, abrupt transitions also exist.These transition zones are extremely important from an ecological and economic point of view. They are very, very rich in biodiversity. Because of this richness and the fact complex conditions exist in this zone, it is vital for the economy of that region.

In this post, I’ll take a look at the abrupt changes from one ecosystem to another. We’ll also see what these abrupt changes cause and how that is important for life in that region. These regions have faced great damage due to human activities. Understanding their dynamics is important if we are to manage them better in the future.

Continue reading Ecotones and edges: Explaining abrupt changes in ecosystems

Homeostasis: It’s why you tilt bikes, it’s why populations never grow forever

This is the second post in the “feedback loops” series.

In the first blog of this series, I started the post by talking about how our body responds to cold and hot conditions. When it gets too cold, we shiver to increase the body temperature. When it gets too hot, we sweat.  The sweat evaporates off of our skin and cools our body.

Both these phenomena are the most common examples of a natural process called Homeostasis. Even though temperature regulation in mammals is considered the most common form of homeostasis in the living world, it is not the only one. There are some fascinating examples of homeostasis in our everyday life as well as the ecosystem at large. In this post, we’ll take a look at some of them.

Continue reading Homeostasis: It’s why you tilt bikes, it’s why populations never grow forever