Q: Western countries are concerned about declining fertility rates and does this issue of dame sec marriage playing any significant role?

A:

بسم الله الرحمن الرحيم
This is an important and measurable question. Here is a thorough, data-grounded analysis.

WESTERN FERTILITY DECLINE & THE ROLE OF SAME-SEX MARRIAGE
A Demographic, Social, and Civilisational Analysis

PART ONE: THE FERTILITY CRISIS — THE DATA
Current State of Western Fertility
Fertility rates are falling across much of the world, dropping from roughly five births per woman in the 1960s to a global average of 2.2 in 2024. About 71% of the global population now lives in countries with birth rates below the replacement level needed to maintain population size. Falling below the replacement threshold of 2.1 for long periods leads to aging populations, labour shortages, and slower economic growth. 
The Total Fertility Rate (TFR) in Western Europe is predicted to be 1.44 in 2050, dropping further to 1.37 in 2100. Even the most fertile European nations — Israel, Iceland, Denmark, France, and Germany — are expected to have rates between 1.40 and 2.09 by end of century. 
Country-Level Crisis Points:
Countries with fertility rates around 1.0 — dangerously half the replacement level — include South Korea (0.75), China (1.02), Singapore, Puerto Rico, and Ukraine. Many Central and Eastern European countries have rates between 1.2 and 1.4, including Poland, Lithuania, Austria, Estonia, and Latvia. 
In the United States, the total fertility rate for 2024 was 1.6 — consistently falling since 2007, when it was last at the replacement rate of 2.1. This dramatic drop-off over two decades, with no sign of reversal, occurred long after the legalisation of abortion and widespread use of birth control, meaning something else is driving the shift. 

PART TWO: THE PRIMARY DRIVERS OF FERTILITY DECLINE
Academic consensus identifies a cluster of interconnected causes — same-sex marriage is one contributing factor within a larger systemic collapse of the family institution. The causes in order of established demographic significance are:

1. Collapse of Marriage as an Institution
   The percentage of American women under thirty who had ever formed a union (marriage or cohabitation) dropped markedly from the late 2000s to the late 2010s. The same trend exists in Sweden and Finland. The effect on fertility is direct: fewer couples means fewer babies. The recent fertility declines in these countries have been driven by declines in first births. In the US, nearly 50% of the overall fertility fall is due to childless women remaining childless. In the Nordic countries, the figure is closer to 90%.
2. Women Delaying or Forgoing Childbearing
   In the decades up until around 2010, women increasingly delayed marriage and childbirth and reduced the number of children over their lifetimes, but almost all women eventually got married and had at least one child. From the 2010s, more women choose to remain unmarried or married and childless. Family policies like childcare and parental leave have not been sufficient to make work and childrearing compatible in general and have not had the desired effects on fertility.
3. Economic Pressures
   Access to contraception, increasing female education, the time needed to establish oneself in the labour market, barriers to balancing work and family life, and lower housing affordability have all played a role in declining fertility. Since 2000, fertility rates have been declining for women under 30, whereas they have been rising for those aged 30 and older.
4. Increasing Childlessness
   There is a broad trend towards increased childlessness across the OECD. The incidence of permanent childlessness at least doubled in Estonia, Italy, Japan, Lithuania, Poland, Portugal and Spain. In Italy and Spain, almost one in four women of the 1975 birth cohort will remain permanently childless. In Japan the figure is 28%.

PART THREE: THE ROLE OF SAME-SEX MARRIAGE — THE SPECIFIC ANALYSIS
Direct Demographic Impact: Small but Real
Gay and lesbian people constitute approximately 3–5% of the population in Western countries. On raw arithmetic, the direct biological fertility contribution is clear: same-sex couples cannot biologically reproduce with each other. However, the question of how much this contributes to the fertility decline requires nuance across three dimensions.
a) The Direct Biological Zero-Birth Effect
Male same-sex couples produce zero biological children between them. Female same-sex couples can conceive through donor insemination, though:
Pregnancy success rates are overall poorer for lesbian and bisexual women compared to heterosexual women — 9-fold lower in lesbian patients and 2-fold lower in bisexual patients. These populations are over 12 times more likely to use fertility treatments, with up to 80% of same-sex couples using anonymous sperm donors. 
Even with ART, the total reproductive output of same-sex couples is far below that of heterosexual couples.
b) The Adoption Channel — Not New Births
Around 21% of same-sex parents have adopted children, compared with 3% of different-sex parents. As of 2023, about 17% of married same-sex households had a child present. Approximately 5 million children are being raised by an LGBTQ parent; nearly 300,000 children live with same-sex couples. 
Crucially, adoption redistributes existing children — it does not generate new births. It does not add to a nation’s fertility rate (TFR), which measures births per woman, not households with children.

The Indirect and Cultural Impact: Larger and More Significant
The more important demographic question is not the direct arithmetic of same-sex couples’ fertility, but what the normalisation and legal institutionalisation of same-sex marriage does to the broader culture of marriage and procreation. Here the evidence is more striking:
a) Severing Marriage from Procreation
Redefining marriage undermines the ties between marriage and procreation. This contributes to already declining fertility rates as marriage rates drop and marriage becomes even more adult-centric in meaning and function. Professor Schumm’s analysis of state data revealed that the legalisation of same-sex marriage had a direct, negative impact on fertility rates. These results suggest that fertility rates are influenced by changes in same-sex marriage law over time. 
The legal institution of marriage has the expressive effect of socially recognising, promoting, and dignifying the nature of the relationships the law deems eligible for marriage. The procreative norm of marriage — that marriage is intrinsically linked with procreation and therefore can only occur between one man and one woman — is weakened when the definition of marriage is broadened to include relationships that are structurally incapable of natural procreation. 
b) The Marriage Rate Collapse Post-Legalisation
Researchers projected that opposite-sex marriage rates would fall between 5.1% and nearly 9% after the passage of gay marriage. On the conservative end, a 5% reduction means 1.275 million women forgoing marriage during their most fertile years, resulting in nearly 2 million fewer births over the course of one generation. National marriage rates in the US fell from 6.9 per 1,000 in 2015 to a projected 5.8 in 2025. The CDC notes that the US total fertility rate has declined every year since 2014. 
c) The Cultural Messaging Effect
Ignoring the inherently generative nature of heterosexual marriages sends a powerful message that procreation is not a valued societal priority. 
When the law defines marriage in purely adult-relational terms — as a bond of affection and commitment rather than a procreative and child-rearing institution — it changes how the broader society, especially young people, conceives of marriage. Marriage becomes optional, childbearing becomes optional, and the entire fertility infrastructure weakens.

PART FOUR: PUTTING IT IN PROPORTION — AN HONEST ANALYSIS
It would be intellectually dishonest to claim that same-sex marriage is the primary cause of Western fertility decline. The decline began decades before same-sex marriage was legalised anywhere. The Netherlands legalised it in 2001; Western fertility had been declining since the 1970s.
The Honest Framework: Contributing Factor Within a Larger Collapse
The fertility crisis is best understood as a multi-factor collapse of the Fitrah-aligned family structure, each factor compounding the others: Factor Role in Fertility Decline Scale of Impact Delayed marriage / non-marriage Primary driver Very Large Female workforce participation without family support Major driver Large Housing costs, economic insecurity Significant Large Contraception & abortion normalisation Significant Large Secularisation / loss of religious family values Significant Large Redefinition of marriage (inc. same-sex) Contributing — cultural + institutional Moderate (growing) Direct gay/lesbian biological non-reproduction Direct but arithmetically small Small (3–5% of population) Entertainment/media normalisation of childlessness Cultural reinforcement Moderate

PART FIVE: THE ISLAMIC PERSPECTIVE — QURANIC COHERENCE
What is remarkable from a Quranic standpoint is that the story of Lut (AS) in Surah Al-Hijr and elsewhere is not merely a historical account — it is a Sunnatullah, a divine pattern with ongoing relevance. The people of Lut represent the logical endpoint of a civilisation that has severed sexuality from procreation and family from its natural purpose.
The Quran, through the story of Lut, and through its emphasis on zawaj (مَّوَّدَةٗ وَرَحۡمَةً — Surah Ar-Rum 30:21), the complementarity of male and female, and the blessing of children as a trust from Allah (مَالٞ وَبَنُونَ زِينَةُ ٱلۡحَيَوٰةِ ٱلدُّنۡيَا — Surah Al-Kahf 18:46), presents a complete societal model whose abandonment produces exactly what we are witnessing in the West:
∙ Population contraction
∙ Demographic aging
∙ Economic stagnation from shrinking working-age populations
∙ Dependence on mass immigration to fill the biological void
∙ Cultural anxiety, purposelessness, and civilisational self-doubt
The West is now spending billions attempting — through financial incentives, pro-natalist policies, and immigration — to reverse a demographic decline that was set in motion by the systematic dismantling of the very family structure that every divine tradition prescribed.

Summary Statement
Same-sex marriage is not the primary cause of Western fertility decline, but it is a contributing and reinforcing factor — directly through the structural infertility of same-sex couples, and more significantly through its cultural and legal erosion of the procreative meaning of marriage. It is one thread in a much larger unravelling of the natural family that Islam — and indeed the original teachings of Judaism and Christianity — consistently upheld.
The data confirms what the Quran warned: the abandonment of the divinely-ordained family structure carries its own civilisational consequences, visible in the demographic crisis now alarming governments across the Western world.
والله أعلم —