by Rick O'Connor | May 2, 2025
There are numerous websites that show the human population numbers changing “real time” – the last single digit constantly changing – possibly as fast as 4 new humans every second. How do we slow this down?
As we mentioned in the last article, other creature populations respond by either slowing/stopping reproduction or having members of the population disperse to new territories to reduce the pressure on the resources. Sometimes conflict is the response. There was one study where researchers had a space with a fixed area. Within this they place a small population of rats. They provided the rats with “X” amount of food and “X” amount of water each day. At first, the amount of food and water was more than enough to support them. As the population increased (and rats have a high growth rate) the researchers did not increase the amount of food and water – there began to be conflicts within the population – they began to fight – sometimes killing each other.
Homo sapiens have already dispersed to every corner of the planet. There are a few islands, and the continent of Antarctica, we have not colonized – but there is little space for us to disperse more. During my life I have heard discussions about colonizing the ocean floor and the moon. People have talked about sending humans to Mars to deal with the overflow. There have been experiments and trials to determine whether we could do this. I know one marine scientist who lived on the bottom of the Caribbean for several months with others to “test” whether this would work. He mentioned the crowded space did begin to wear on them. He said at one point they were using masking tape to mark off individual’s space – even for their toothbrush. I read about someone who lived in a cave for one year to see if they could live on the bottom of the ocean with only artificial light for the same amount of time. There is the famous Biosphere 2 Project where they placed humans within a closed system to determine where we could inhabit Mars. Humans have already spent much time in space orbiting Earth. In each case there were physical and psychological problems. It is still to be determined whether these dispersal ideas will work.
Biosphere 2
Photo: University of Arizona
If dispersal is not the answer, then slowing population growth would be the next thing to address. Many developed countries have slowed their growth. Much of this has to do with more people going into professions that require college degrees – others are getting married later in life and having fewer children. Much of it has to do with the role change for women. More women are going to college and becoming professionals themselves – delaying marriage and the number of children even further. The growth rate in Europe has slowed dramatically. It has not surpassed 1% since 1961 and has slowed each year since. The reasons can be attributed to those just mentioned – but Europe also has limited space. Asia’s population growth rate has also declined, reaching less than 1% in 2016 – though it varies from one country to another. South America also began a decline in the 1960s and is currently below 1%. But the story in Africa is a little different. Though there has been a decline in the growth rate, it did not start until around 2015 and is still above 2%.
The idea of “just stop having kids” is not as simple as you might think. I was asked when I was teaching this course “Why are the birth rates are so high in developing countries where resources are already stretched?” It is a fair question, but you must also understand how life works in some of these countries. Many have large families to help run the farm or business, they cannot afford to hire labor. I had a student from such a country in a class for one semester and he agreed. He said his father ran a garage and his mother ran the restaurant attached to it. His brothers and sisters were the employees. In some cultures, particularly in the developing world, women are not going to school. The children take care of the elderly and so families need to have employed sons to take care of them. Knowing that health programs are not what they are in the developed world, parents will have several sons to make sure at least one survives long enough to land a good career and be able to support them. Daughters do not help – so, they will continue to have children until this need is met. In many of these cultures the daughters are expected to marry into money to help take care of them in their old age – and in some cases the daughters are expected to have sons as well – as early, and as many, as possible to prepare.
China had their famous “one-child only” policy, which began in 1979. The purpose was to slow their growth rate and stabilize their enormous population. Under this plan Chinese families were to have only one child, with fines assessed for any additional children. Similar to other cultures, a couple would be expected to take care of both parents, and both sets of grandparents. Under the one-child policy, this became a huge burden for a single couple. In 2009 China changed the policy to where couples who had no siblings could have two children at no penalty. There was the added problem of your only child being a female. Females would be married off to another family leaving no one to support her parents. China did relax the laws in such cases to allow extra children in hopes of having a son. Under this new policy in 2016 there were 17.9 million babies born in China – a record for the 21st century. The growth rate has declined some since. Some of this has to do with the cost of raising a child in China.
I used to show a film to my students addressing this issue. In one part it showed an elementary school in Japan from the outside. The camera slowly circled the school until you see the front door – the camera goes in. As you go down the hallways, the classrooms are empty – until you reach this one classroom. Within in sits a single 5th grade boy – he is the only student in the entire school. This showed how dramatic the population decline in Japan had become. The problem here was similar to China’s – who would take care of the elderly. This system is different though that in Japan the elderly are often taken care by a “social security” type system. Young employed people pay a tax that supports the care of the elderly. With no young workers, there are no taxes, and elderly care became a problem. This system had to be changed.
One response to this problem has been paying families to have more children. In some countries this has been in direct payments to the parents, in others it has been in the form of free childcare, paid time off for family needs, etc. According to one report – this has not helped – birth rates continue to decline. Part of this is a social issue, today’s young generation is not as interested in having large families, or families at all. In the United States there has been a drop in birth rates, but this has not impacted us as much due to immigrants moving in and filling that niche. This may be changing now.
The human population story is a very complicated and interesting one. From a “natural history” side we understand the need to slow the growth rate. From a cultural/economic one, we understand why/how this can be problematic. Either way the large number of humans on the planet are stressing our resources. The next few articles in this series will look at what resources we need to survive and how we are managing them.
References
Worldometer. https://www.worldometers.info/world-population/.
Annual Population Growth Rate of Europe; 1950-2023. Statista. https://www.statista.com/statistics/1251591/population-growth-rate-in-europe/#:~:text=The%20population%20of%20Europe%20decreased,and%20between%202020%20and%202023..
Population Growth in Latin America and the Caribbean Falls Below Expectations and Region’s Total Population Reaches 663 Million in 2024. The United Nations. https://www.cepal.org/en/pressreleases/population-growth-latin-america-and-caribbean-falls-below-expectations-and-regions.
Population Growth Rate in Africa From 2000 to 2023. Statista. https://www.statista.com/statistics/1224179/population-growth-in-africa/.
Two Child Policy. Wikipedia. https://en.wikipedia.org/wiki/Two-child_policy#:~:text=From%202016%20to%202021%2C%20it,for%20exceeding%20them%20were%20removed..
North, A. 2024. You Can’t Even Pay People to Have Kids. Population Connection. https://populationconnection.org/article/you-cant-even-pay-people-to-have-more-kids/#:~:text=Other%20countries%20have%20tried%20direct,of%20around%20%2430%2C000%20to%20newlyweds.
by Rick O'Connor | Apr 25, 2025
Everyone has heard of sponges, and many know they grow in the ocean. But fewer are aware that sponges are actually animals. When we think of animals, we think of something that crawls around seeking food and laying eggs periodically. Sponges are not like that. They are “blob” looking creatures sitting on the ocean floor. At first glance you might call them fungi, or maybe some weird form of algae – but they are animals, the simplest form of animal life on the planet.
A vase sponge.
Florida Sea Grant
What makes them animals is the lack of cell walls and chlorophyll. Fungi also lack chlorophyll, but they do possess cell walls – so, are classified differently. Because animals lack chlorophyll they cannot produce their own food – and must consume creatures in order to obtain their needed sugars. So, what do sponges “hunt”? They feed on plankton in the water column – many of the microscopic creatures we have already written about in this series.
The sponge body is basically a colony of individual ameboid and flagellated cells. These small cells attach to the substrate and begin to reproduce sexually and asexually to form the colony. As they grow, they form a series of pores found on the exterior of the mass. The flagellated cells – called collar cells – move their flagella to generate a current. This current draws in seawater – along with its plankton – where the colony, both the flagellated and ameboid cells, feed. As the colony grows the exterior pores lead to channels and canals where the cells live and eventually empty into a larger cavity known as the atrium. Here the water moves upward and exits the sponge through an opening called the osculum. Waste from feeding exits the sponge through the osculum as well.
The anatomy of a sponge.
Flickr
As the colony grows it is supported by a series of tiny spike-like structures called spicules. Spicules are made of different materials and are one method of separating and classifying the different sponges. One group of sponges are known as the calcareous sponges – their spicules are made of calcium carbonate and are rough to the touch. Another group are known as the “glass” sponges – their spicules are made of silica and are sharp-prickly to the touch. A third group are known as the bath sponges – their spicules are made of a softer material called spongin. It is this third group that was used for centuries for both bathing and washing.
Glass sponges are beautiful.
Photo: NOAA
These simple creatures play an important role in the ecology of marine systems. As filter feeders, they remove material from the water column improving water clarity and quality. They remove excess nitrogen and play a role in the carbon cycle. They provide habitat for numerous small marine creatures where they can hide from predators and find food.
Sponges need a hard substrate to grow on and thus are more abundant in the coral reefs of south Florida. Locally I have only found them in the seagrass beds. But there they do play the same ecological role you would find them doing on coral reefs. They are one of the less encountered creatures of the northern Gulf.
by Rick O'Connor | Apr 11, 2025
Following the textbook I used when I was teaching environmental science there were 6.7 billion humans on the planet in 2011. I remember when we hit 6 billion. There was a lot made of it in the media. Currently (2025) we are at 8 billion. The textbook I used was published in 2011 – which means we have seen a growth of 2 billion people over 14 years – that’s a net gain of 143 million each year – 12 million each month – 400,000 a day – 17,000 an hour – 275 each minute – a net gain of 4 humans every second. Our population growth rate is astounding.
There are nearly 8 billion people on the planet today.
Photo: University of Central Florida
The calculation used to measure population change over time is relatively simple.
Population change = (births + immigration) – (deaths + emigration)
The natural history of creatures on our planet follows the same basic principle. There is a correlation between the number of offspring produced and the amount of parental care provided. The goal of each parent of any species is to have at least one of your offspring reach sexual maturity. Those who give very little parental care – trees, grasses, sea turtles, jellyfish, etc. – will produce large numbers of offspring knowing that over 90% will not make it – many will not make it past the first few days. Those who produce few offspring – songbirds, manatees, and gorillas – provide parental care to assure at least one makes it. Some will provide parental care for a few days, or a few weeks, others will provide it for a few years. BUT even those who show parental care typically produce 2-3 offspring knowing that a couple will not survive.
This nest of birds has three chicks. Not all will survive.
Photo: Rick O’Connor
This is a piece of the population control story. It does not benefit any species to have an overpopulation problem. I had to take an oral examination to complete my graduate degree. You are in a chair facing a long table full of professors who are asking you all sorts of questions. One question was “who is a rhinoceros’ greatest competitor?” Being very nervous I was bumbling and fumbling in my brain trying to figure WHO would be their biggest problem… and then – it came to me… another rhinoceros. They want the same space, the same resources, and the same mates as you. Competition begins day one. Over population is a problem for everyone. Other things that effect the number of newborns from reaching sexual maturity are predators and disease. In some species even the parents (typically the father) may be a predator – and will kill their own offspring (polar bears).
Placing humans in this model – we will see that typically there is only one offspring produced. Parents must do all they can to help this offspring reach sexual maturity. For Homo sapiens females reach sexual maturity between the ages of 8 and 13, 9 and 14 for males. In many cultures this is when the parent’s job is over and the child either enters an apprenticeship or gets married. Most cultures do not recognize “adulthood” until the age of 18. So… your job as a parent is to make sure they reach that age.
For most of our history environmental factors played a role in controlling population growth – namely disease. 200+ years ago, many children did not survive childbirth or died early from diseases. But things have changed.
It took from the time humans arrived on the planet to 1927 for us to reach 2 billion humans. It took less than 50 years to add the next 2 billion (1974), and only 25 years at add the next 2 billion (1999). The textbook I used stated we will reach 7 billion by 2012 – we reached it in 2011. They are expecting 9.7 billion by the year 2050.
What happened? What changed to create such a large exponential growth in the human population? The answer lies on both sides of the population change equation – more births are making it to puberty and less people are dying. Modern medicine has done miracles in improving overall human health on both ends – and this is wonderful news, but it does come with a cost. As with any species population – there is only so much space and resources. When the population of a species begins to stress this – many creatures will cease (or slow) reproduction. Another answer we see is dispersal – members of the population will move to new locations and build new populations reducing the stress on the resources. As we mentioned in a previous article – they will spread across the landscape until they reach a barrier that stops them from going further. But in nature the role of predators and disease has not gone away as it has with humans. The current growth rate for humans is 1.1% but has been slowly declining since the 1960s.
This brings up the question of carrying capacity (K) – the maximum number of individuals a population’s space and resources can support. As we mentioned, when K is reached in the natural world species either slow reproduction, disperse, or both. But what IS the carrying capacity for humans on this planet? The textbook I used mentioned there was no consensus on this. Some were saying as low as 2 billion – which we know was not accurate, though some would say some parts of the world are already in a population crisis. Others say it may be as high as 30 billion. A quick search on the internet finds the following…
- The AI response states somewhere between 9-10 billion.
- The Australian Academy of Science states it could be between 500 million and 1 trillion.
- The Population Connection states it is between 500 million and 1 sextillion (21 zeros).
Bottom line – we do not know – it depends on which model you use and how you view/term a functioning population. When I was teaching the class, most models stated somewhere between 10-15 billion.
As we mentioned, when you are reaching carrying capacity – most will either slow/stop reproduction or disperse. In our next article, we will look at how humans might address this problem.
References
Miller, G.T., Spoolman, S.E. 2011. Living in the Environment. Brooks/Cole Cengage Learning. Belmont CA. pp. 674.
Puberty and Precocious Puberty. Eunice Kennedy Shiver Institute of Child Health and Human Development. https://www.nichd.nih.gov/health/topics/puberty.
Population. United Nations. https://www.un.org/en/global-issues/population.
Human Population Growth. Libretexts. https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/General_Biology_(Boundless)/45%3A_Population_and_Community_Ecology/45.04%3A_Human_Population_Growth/45.4A%3A_Human_Population_Growth.
How Many People Can the Earth Actually Support? Australian Academy of Science. https://www.science.org.au/curious/earth-environment/how-many-people-can-earth-actually-support.
What is the Carrying Capacity of Earth? The Population Connection. https://populationconnection.org/blog/carrying-capacity-earth/.
by Rick O'Connor | Apr 11, 2025
As we mentioned when we began writing about seaweed, seaweed and seagrass are very different. Seagrasses are true plants in the sense that they have an internal vascular system that runs water and other material throughout the plant. Like the artery and veins of animals – they are called xylem and phloem. Water in the soil is diffused through the tissue of the roots into the xylem, which moves the water up through the stem to the leave where it is used in photosynthesis. The sugars produced by photosynthesis are moved through back down into the plant by traveling through the phloem. Seagrasses produce small flowers that are pollinated by dispersing the pollen in the currents and by small invertebrates, such as amphipods and polychaetae worms. Seagrasses are true plants.
Grassbeds are also full of life, albeit small creatures.
Photo: Virginia Sea Grant
Believed to have originated as land plants, today there are about 72 species of seagrasses found around the world; seven are found in Florida; five found in the Pensacola Bay system. Though found in some open ocean systems, most seagrass beds are found in the protected waters of the estuary. They thrive in areas with low wave energy and clear water. They help stabilize the shoreline and remove pollutants from the water column. There is an abundance of marine creatures who use the seagrass beds as either a source of food, or habitat. It has been determined that at least 80% of the commercially important finfish and shellfish use seagrass beds for at least part of their life cycle.
Three of the five local species can be found in Santa Rosa Sound. Shoal grass (Halodule) has a flat blade but is very thin, between 2-3mm wide. Because it is so narrow, less surface area, it can tolerate waves better than turtle grass, and thus lives closer to the shoreline. Within the shoal grass you can find a variety of small baitfish feeding, as well as blue crabs and hermit crabs scavenging. But it does not provide the hiding spaces that the wider blade turtle grass does.
Shoal grass. One of the common seagrasses in Florida.
Photo: Leroy Creswell
Turtle grass (Thalassia) have blades that are 10mm wide. These wider blades do not handle the waves as well and thus turtle grass grows in deeper waters further off the beach. How deep they can grow is a function of the amount of sunlight reaching the bottom. In the Florida Keys turtle grass has been found at depths of 30 feet. Locally maximum depths are more likely near 10 feet. The wide blades of this grass provide surface area for a variety of small algae and invertebrates to attach. These epiphytes and epizoids are a major player in the food web of seagrass beds. Numerous invertebrates and fish feed on this “scum layer” found on the grass blades. The grazers attract low level predators such as pinfish, puffers, and sea horses. These in turn attract larger predators such as rays, speckled trout, and flounder. Manatees and sea turtles can be found here as well as sharks and the occasional bottled nose dolphin.
The wide blades of turtle grass provide habitat for a variety of epibiota.
Photo: UF IFAS
Manatee grass (Syringodium) resembles shoal grass, but the blade is round instead of flat. It can be found forming its own patches or dispersed within the other species. The abundance of this species seems to be increasing in local waters.
Gracilaria is a common epiphytic red algae growing in our seagrass beds. Photo: Rick O’Connor
Widgeon grass (Ruppia) is a common seagrass found in the upper portions of our estuary. Though it can live in the higher salinities near Pensacola Beach, it can also tolerate the lower salinities of the upper bays and thus, with less competition, does very well here. It also resembles shoal grass but differs in that the blade branches as it grows. Like all seagrass beds, widgeon grass can support a lot of marine creatures and increase the overall biodiversity of the bay.
The branched leaves of the widgeon grass.
Since the 1950s the northern Gulf coast has witnessed a decline in seagrass acreage. The decline was caused by a combination of factors. One, increased sedimentation with stormwater and development. In some cases, the seagrass was literally buried and in others the sediment decreased water clarity which decreased needed sunlight. Two, shrimp trawls. At one time shrimpers could pull their trawls through the grass to catch shrimp. This ripped and destroyed much of the habitat and the state closed shrimping in all grassbeds. Three, seawalls. Waves reflecting off the seawalls increased the wave energy within the Sound to a point that seagrass could not tolerate it. The landward edge of many grassbeds began to retreat from these seawalls reducing the overall acreage of the seagrass bed. Four, prop scars. Boats running through the grassbeds will cut deep scars in the grass that reach the sand beneath. It can take up to 10 years for the system to restore itself. And, with more boats out there, there are more scars. Five, the increase in the mass of drift algae settling on the grasses. These drift algae populations increase with increased nutrients being discharged into the Sound from land-based run-off. Drift algae cover the grasses decreasing their ability to absorb much needed sunlight.
Monitoring in recent years has shown that our seagrasses are trying to restore themselves and some beds have increased in size during the last couple of decades. Monitoring continues.
References
Florida Seagrass. Florida Department of Environmental Protection. https://floridadep.gov/rcp/seagrass.
Potouroglou, M., Pedder, K., Wood, K., Scalenghe. 2022. What to Know About Seagrass, the Ocean’s Overlooked Powerhouse. World Resources Institute. https://ocean.si.edu/ocean-life/plants-algae/seagrass-and-seagrass-beds#:~:text=Seagrasses%20produce%20the%20longest%20pollen,flower%20and%20fertilization%20takes%20place.
Seagrass and Seagrass Beds. Ocean, Find Your Blue. Smithsonian National Museum of Natural History. https://ocean.si.edu/ocean-life/plants-algae/seagrass-and-seagrass-beds#:~:text=Seagrasses%20produce%20the%20longest%20pollen,flower%20and%20fertilization%20takes%20place..
Seagrass Species Profiles. South Florida Aquatic Environments. Florida Museum of Natural History. https://floridadep.gov/rcp/seagrass.
by Rick O'Connor | Mar 28, 2025
Evidence suggests that Homo sapiens’ initial population originated in east Africa – though some think we may have originated in southern Africa, and others from northwest Africa. It is believed this occurred about 300,000 years ago. The first humans were hunter gathers and fed primarily on small prey and plants – we are omnivorous. With the development of stone tools early humans could feed on larger prey and take a different position in the food chain.
Evidence suggest that humans originated in Africa and began their dispersal across the planet from there.
Image: BBC.
Populations of all creatures increase and decrease due to the number of births, deaths, immigration, and emigration within their populations (we will focus more on the human population in the next article). As populations grow, competition for needed resources increases. One response to this competition is dispersal – the movement of members of a population to a new location where resources can be found. This is different than migration in that in dispersal the members do not return – they have moved away.
Evidence suggests that humans began dispersing from Africa very early. It was thought at first humans did move into southern Africa, but there was a mass movement north into the Middle East. From here humans began to move east along southern Asia to India and beyond to southeast Asia. There is evidence of “island hopping” as they made their way across Indonesia and eventually to Australia. Later groups from southern Asia dispersed north into northern Asia. From here there were two movements – one into Europe and another across an exposed landmass connecting Asia to North America – remember the Earth continues to go through slow change over time. At one time there was a land bridge that connected the two continents and allowed humans, and other species, to cross. Humans began to spread across North America and – with the emergence of a land bridge in Central America – reached South America. There are those who also believe – based on language and culture – some Polynesian humans reached South America by boat. To test this idea an expedition sailed from Polynesia to South America on a balsa wood raft called Kon Tiki in the 1940s. This same team attempted to sail from Africa to South America to show this could have been a dispersal route as well using boat materials from that time – but that expedition failed. However they reached South America, they did – and humans had dispersed to cover all landmasses except Antarctica. This still holds true – there are no native populations of humans on the Antarctic continent – only visitors.
This shows possible dispersal routes of humans out of Africa.
Image: Newsweek.
Within each region of the planet where humans have inhabited, we find physical and cultural differences. The physical difference – which we call races today – were adaptations to the environment where they lived. There languages, tools and building practices, songs and instruments, and religions were all born from the area where they lived. Many of these populations were isolated from each other – and so their cultures became quite different. As these populations grew and expanded, they would come in contact with each other. Many times, these different cultures, or tribes, would fight for resources and space. As our imaginations and technologies grew, some cultures were able to cover more territory and conflicts increased.
Today there are about 8 billion humans on the planet. Some areas are more densely populated than others. Based on the website Worldometer – we are gaining a new human almost every second.
Over history, most species have had a slower population growth – if growing at all. Numbers are kept under control by predators, disease, and environmental conditions that impede, or restrict, reproduction. But not with humans. In the next article we will look closer at the cause of the human population explosion.
References
Pavid, K. 2018. Rethinking Our Human Origins in Africa. Science News. Natural History Museum. https://www.nhm.ac.uk/discover/news/2018/july/the-way-we-think-about-the-first-modern-humans-in-africa.html.
Pobinar, B. 2013. Evidence for Meat-eating by Early Humans. Nature Education Knowledge. (46)1. https://www.nature.com/scitable/knowledge/library/evidence-for-meat-eating-by-early-humans-103874273/#:~:text=Tooth%20morphology%20and%20dental%20microwear,Ungar%202000%3B%20Luca%20et%20al..
Dorey, F., Blaxland, B. 2020. The First Migrants Out of Africa. Australian Museum. https://australian.museum/learn/science/human-evolution/the-first-migrations-out-of-africa/.
Kon Tiki Expedition. Wikipedia. https://en.wikipedia.org/wiki/Kon-Tiki_expedition.
Worldometer. https://www.worldometers.info/world-population/.
